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YOUR PRACTICAL, HANDS-ON GUIDE TO WRITING APPLICATIONS USING GOGoogle announced the Go programming language to the public in 2009, with the version 1.0 release announced in 2012. Since its announcement to the community, and the compatibility promise of the 1.0 release, the Go language has been used to write scalable and high-impact software programs ranging from command-line applications and critical infrastructure tools to large-scale distributed systems. It's speed, simplicity, and reliability make it a perfect choice for developers working in various domains.In Practical Go - Building Scalable Network + Non-Network Applications, you will learn to use the Go programming language to build robust, production-ready software applications. You will learn just enough to building command line tools and applications communicating over HTTP and gRPC.This practical guide will cover:* Writing command line applications* Writing a HTTP services and clients* Writing RPC services and clients using gRPC* Writing middleware for network clients and servers* Storing data in cloud object stores and SQL databases* Testing your applications using idiomatic techniques* Adding observability to your applications* Managing configuration data from your applicationsYou will learn to implement best practices using hands-on examples written with modern practices in mind. With its focus on using the standard library packages as far as possible, Practical Go will give you a solid foundation for developing large applications using Go leveraging the best of the language's ecosystem.

Practical Go: Building Scalable Network and Non-Network Applications

Introduction xviiGetting Started xxiChapter 1 Writing Command-Line Applications 1Your First Application 1Writing Unit Tests 8Using the Flag Package 14Testing the Parsing Logic 20Improving the User Interface 22Removing Duplicate Error Messages 23Customizing Usage Message 24Accept Name via a Positional Argument 25Updating the Unit Tests 28Summary 32Chapter 2 Advanced Command-Line Applications 33Implementing Sub-commands 33An Architecture for Sub-command-Driven Applications 37Testing the Main Package 43Testing the Cmd Package 45Making Your Applications Robust 47User Input with Deadlines 48Handling User Signals 52Summary 56Chapter 3 Writing HTTP Clients 57Downloading Data 57Testing the Data Downloader 59Deserializing Received Data 61Sending Data 66Working with Binary Data 72Summary 80Chapter 4 Advanced HTTP Clients 81Using a Custom HTTP Client 81Downloading from an Overloaded Server 81Testing the Time-Out Behavior 85Configuring the Redirect Behavior 88Customizing Your Requests 91Implementing Client Middleware 92Understanding the RoundTripper Interface 93A Logging Middleware 94Add a Header to All Requests 96Connection Pooling 99Configuring the Connection Pool 103Summary 104Chapter 5 Building HTTP Servers 105Your First HTTP Server 105Setting Up Request Handlers 108Handler Functions 109Testing Your Server 112The Request Struct 114Method 115URL 115Proto, ProtoMajor, and ProtoMinor 116Header 116Host 116Body 116Form, PostForm 116MultipartForm 117Attaching Metadata to a Request 118Processing Streaming Requests 121Streaming Data as Responses 126Summary 132Chapter 6 Advanced HTTP Server Applications 133The Handler Type 133Sharing Data across Handler Functions 134Writing Server Middleware 139Custom HTTP Handler Technique 139The HandlerFunc Technique 140Chaining Middleware 142Writing Tests for Complex Server Applications 147Code Organization 147Testing the Handler Functions 153Testing the Middleware 155Testing the Server Startup 157Summary 159Chapter 7 Production-Ready HTTP Servers 161Aborting Request Handling 161Strategies to Abort Request Processing 165Handling Client Disconnects 169Server-Wide Time-Outs 173Implement a Time-Out for All Handler Functions 173Implementing Server Time-Out 174Implementing Graceful Shutdown 179Securing Communication with TLS 184Configuring TLS and HTTP/2 184Testing TLS Servers 188Summary 192Chapter 8 Building RPC Applications with gRPC 193gRPC and Protocol Buffers 193Writing Your First Service 197Writing the Server 198Writing a Client 203Testing the Server 207Testing the Client 211A Detour into Protobuf Messages 214Marshalling and Unmarshalling 214Forward and Backward Compatibility 219Multiple Services 220Error Handling 226Summary 228Chapter 9 Advanced gRPC Applications 229Streaming Communication 229Server-SideStreaming 230Client-SideStreaming 237Bidirectional Streaming 239Receiving and Sending Arbitrary Bytes 247Implementing Middleware Using Interceptors 256Client-Side Interceptors 257Server-Side Interceptors 263Wrapping Streams 269Chaining Interceptors 271Summary 272Chapter 10 Production-Ready gRPC Applications 275Securing Communication with TLS 275Robustness in Servers 278Implementing Health Checks 278Handling Runtime Errors 286Aborting Request Processing 289Robustness in Clients 297Improving Connection Setup 298Handling Transient Failures 300Setting Time-Outs for Method Calls 305Connection Management 306Summary 309Chapter 11 Working with Data Stores 311Working with Object Stores 312Integration with Package Server 313Testing Package Uploads 323Accessing Underlying Driver Types 325Working with Relational Databases 327Integration with Package Server 328Testing Data Storage 339Data Type Conversions 343Using Database Transactions 346Summary 348Appendix A Making Your Applications Observable 349Logs, Metrics, and Traces 349Emitting Telemetry Data 352Command-Line Applications 352HTTP Applications 360gRPC Applications 364Summary 366Appendix B Deploying Applications 367Managing Configuration 367Distributing Your Application 370Deploying Server Applications 372Summary 373Index 375 xiii Contents Introduction xvii Getting Started xxi Chapter 1 Writing Command-Line Applications 1 Your First Application 1 Writing Unit Tests 8 Using the Flag Package 14 Testing the Parsing Logic 20 Improving the User Interface 22 Removing Duplicate Error Messages 23 Customizing Usage Message 24 Accept Name via a Positional Argument 25 Updating the Unit Tests 28 Summary 32 Chapter 2 Advanced Command-Line Applications 33 Implementing Sub-commands 33 An Architecture for Sub-command-Driven Applications 37 Testing the Main Package 43 Testing the Cmd Package 45 Making Your Applications Robust 47 User Input with Deadlines 48 Handling User Signals 52 Summary 56 Chapter 3 Writing HTTP Clients 57 Downloading Data 57 Testing the Data Downloader 59 Deserializing Received Data 61 Sending Data 66 COPYRIGHTED MATERIAL xiv Contents Working with Binary Data 72 Summary 80 Chapter 4 Advanced HTTP Clients 81 Using a Custom HTTP Client 81 Downloading from an Overloaded Server 81 Testing the Time-Out Behavior 85 Configuring the Redirect Behavior 88 Customizing Your Requests 91 Implementing Client Middleware 92 Understanding the RoundTripper Interface 93 A Logging Middleware 94 Add a Header to All Requests 96 Connection Pooling 99 Configuring the Connection Pool 103 Summary 104 Chapter 5 Building HTTP Servers 105 Your First HTTP Server 105 Setting Up Request Handlers 108 Handler Functions 109 Testing Your Server 112 The Request Struct 114 Method 115 URL 115 Proto, ProtoMajor, and ProtoMinor 116 Header 116 Host 116 Body 116 Form, PostForm 116 MultipartForm 117 Attaching Metadata to a Request 118 Processing Streaming Requests 121 Streaming Data as Responses 126 Summary 132 Chapter 6 Advanced HTTP Server Applications 133 The Handler Type 133 Sharing Data across Handler Functions 134 Writing Server Middleware 139 Custom HTTP Handler Technique 139 The HandlerFunc Technique 140 Chaining Middleware 142 Writing Tests for Complex Server Applications 147 Code Organization 147 Testing the Handler Functions 153 Testing the Middleware 155 Testing the Server Startup 157 Summary 159 Contents xv Chapter 7 Production-Ready HTTP Servers 161 Aborting Request Handling 161 Strategies to Abort Request Processing 165 Handling Client Disconnects 169 Server-Wide Time-Outs 173 Implement a Time-Out for All Handler Functions 173 Implementing Server Time-Out 174 Implementing Graceful Shutdown 179 Securing Communication with TLS 184 Configuring TLS and HTTP/2 184 Testing TLS Servers 188 Summary 192 Chapter 8 Building RPC Applications with gRPC 193 gRPC and Protocol Buffers 193 Writing Your First Service 197 Writing the Server 198 Writing a Client 203 Testing the Server 207 Testing the Client 211 A Detour into Protobuf Messages 214 Marshalling and Unmarshalling 214 Forward and Backward Compatibility 219 Multiple Services 220 Error Handling 226 Summary 228 Chapter 9 Advanced gRPC Applications 229 Streaming Communication 229 Server-Side Streaming 230 Client-Side Streaming 237 Bidirectional Streaming 239 Receiving and Sending Arbitrary Bytes 247 Implementing Middleware Using Interceptors 256 Client-Side Interceptors 257 Server-Side Interceptors 263 Wrapping Streams 269 Chaining Interceptors 271 Summary 272 Chapter 10 Production-Ready gRPC Applications 275 Securing Communication with TLS 275 Robustness in Servers 278 Implementing Health Checks 278 Handling Runtime Errors 286 Aborting Request Processing 289 xvi Contents Robustness in Clients 297 Improving Connection Setup 298 Handling Transient Failures 300 Setting Time-Outs for Method Calls 305 Connection Management 306 Summary 309 Chapter 11 Working with Data Stores 311 Working with Object Stores 312 Integration with Package Server 313 Testing Package Uploads 323 Accessing Underlying Driver Types 325 Working with Relational Databases 327 Integration with Package Server 328 Testing Data Storage 339 Data Type Conversions 343 Using Database Transactions 346 Summary 348 Appendix A Making Your Applications Observable 349 Logs, Metrics, and Traces 349 Emitting Telemetry Data 352 Command-Line Applications 352 HTTP Applications 360 gRPC Applications 364 Summary 366 Appendix B Deploying Applications 367 Managing Configuration 367 Distributing Your Application 370 Deploying Server Applications 372 Summary 373 Index 375 NOTE A glossary of relevant terms is available for free download from the book's web page: https://www.wiley.com/go/practicalgo.xiii Contents Introduction xvii Getting Started xxi Chapter 1 Writing Command-Line Applications 1 Your First Application 1 Writing Unit Tests 8 Using the Flag Package 14 Testing the Parsing Logic 20 Improving the User Interface 22 Removing Duplicate Error Messages 23 Customizing Usage Message 24 Accept Name via a Positional Argument 25 Updating the Unit Tests 28 Summary 32 Chapter 2 Advanced Command-Line Applications 33 Implementing Sub-commands 33 An Architecture for Sub-command-Driven Applications 37 Testing the Main Package 43 Testing the Cmd Package 45 Making Your Applications Robust 47 User Input with Deadlines 48 Handling User Signals 52 Summary 56 Chapter 3 Writing HTTP Clients 57 Downloading Data 57 Testing the Data Downloader 59 Deserializing Received Data 61 Sending Data 66 COPYRIGHTED MATERIAL xiv Contents Working with Binary Data 72 Summary 80 Chapter 4 Advanced HTTP Clients 81 Using a Custom HTTP Client 81 Downloading from an Overloaded Server 81 Testing the Time-Out Behavior 85 Configuring the Redirect Behavior 88 Customizing Your Requests 91 Implementing Client Middleware 92 Understanding the RoundTripper Interface 93 A Logging Middleware 94 Add a Header to All Requests 96 Connection Pooling 99 Configuring the Connection Pool 103 Summary 104 Chapter 5 Building HTTP Servers 105 Your First HTTP Server 105 Setting Up Request Handlers 108 Handler Functions 109 Testing Your Server 112 The Request Struct 114 Method 115 URL 115 Proto, ProtoMajor, and ProtoMinor 116 Header 116 Host 116 Body 116 Form, PostForm 116 MultipartForm 117 Attaching Metadata to a Request 118 Processing Streaming Requests 121 Streaming Data as Responses 126 Summary 132 Chapter 6 Advanced HTTP Server Applications 133 The Handler Type 133 Sharing Data across Handler Functions 134 Writing Server Middleware 139 Custom HTTP Handler Technique 139 The HandlerFunc Technique 140 Chaining Middleware 142 Writing Tests for Complex Server Applications 147 Code Organization 147 Testing the Handler Functions 153 Testing the Middleware 155 Testing the Server Startup 157 Summary 159 Contents xv Chapter 7 Production-Ready HTTP Servers 161 Aborting Request Handling 161 Strategies to Abort Request Processing 165 Handling Client Disconnects 169 Server-Wide Time-Outs 173 Implement a Time-Out for All Handler Functions 173 Implementing Server Time-Out 174 Implementing Graceful Shutdown 179 Securing Communication with TLS 184 Configuring TLS and HTTP/2 184 Testing TLS Servers 188 Summary 192 Chapter 8 Building RPC Applications with gRPC 193 gRPC and Protocol Buffers 193 Writing Your First Service 197 Writing the Server 198 Writing a Client 203 Testing the Server 207 Testing the Client 211 A Detour into Protobuf Messages 214 Marshalling and Unmarshalling 214 Forward and Backward Compatibility 219 Multiple Services 220 Error Handling 226 Summary 228 Chapter 9 Advanced gRPC Applications 229 Streaming Communication 229 Server-Side Streaming 230 Client-Side Streaming 237 Bidirectional Streaming 239 Receiving and Sending Arbitrary Bytes 247 Implementing Middleware Using Interceptors 256 Client-Side Interceptors 257 Server-Side Interceptors 263 Wrapping Streams 269 Chaining Interceptors 271 Summary 272 Chapter 10 Production-Ready gRPC Applications 275 Securing Communication with TLS 275 Robustness in Servers 278 Implementing Health Checks 278 Handling Runtime Errors 286 Aborting Request Processing 289 xvi Contents Robustness in Clients 297 Improving Connection Setup 298 Handling Transient Failures 300 Setting Time-Outs for Method Calls 305 Connection Management 306 Summary 309 Chapter 11 Working with Data Stores 311 Working with Object Stores 312 Integration with Package Server 313 Testing Package Uploads 323 Accessing Underlying Driver Types 325 Working with Relational Databases 327 Integration with Package Server 328 Testing Data Storage 339 Data Type Conversions 343 Using Database Transactions 346 Summary 348 Appendix A Making Your Applications Observable 349 Logs, Metrics, and Traces 349 Emitting Telemetry Data 352 Command-Line Applications 352 HTTP Applications 360 gRPC Applications 364 Summary 366 Appendix B Deploying Applications 367 Managing Configuration 367 Distributing Your Application 370 Deploying Server Applications 372 Summary 373 Index 375 NOTE A glossary of relevant terms is available for free download from the book's web page: https://www.wiley.com/go/practicalgo.