book

Go Cookbook

Name: Go Cookbook
Author: Sau Sheong Chang
ISBN: 9781098122119

by Sau Sheong Chang

September 2023

Intermediate to advanced

367 pages

7h 23m

English

O'Reilly Media, Inc.

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Preface
Conventions Used in This BookUsing Code ExamplesO’Reilly Online LearningHow to Contact UsAcknowledgments
1. Getting Started Recipes
1.0. Introduction1.1. Installing Go1.2. Playing Around with Go1.3. Writing a Hello World Program1.4. Using an External Package1.5. Handling Errors1.6. Logging Events1.7. Testing Your Code
2. Module Recipes
2.0. Introduction2.1. Creating a Go Module2.2. Importing Dependent Packages Into Your Module2.3. Removing Dependent Packages from Your Module2.4. Find Available Versions of Third-Party Packages2.5. Importing a Specific Version of a Dependent Package Into Your Module2.6. Requiring Local Versions of Dependent Packages2.7. Using Multiple Versions of the Same Dependent Packages
3. Error Handling Recipes
3.0. Introduction3.1. Handling Errors3.2. Simplifying Repetitive Error Handling3.3. Creating Customized Errors3.4. Wrapping an Error with Other Errors3.5. Inspecting Errors3.6. Handling Errors with Panic3.7. Recovering from Panic3.8. Handling Interrupts
4. Logging Recipes
4.0. Introduction4.1. Writing to Logs4.2. Change What Is Being Logged by the Standard Logger4.3. Logging to File4.4. Using Log Levels4.5. Logging to the System Log Service
5. Function Recipes
5.0. Introduction5.1. Defining a Function5.2. Accepting Multiple Data Types with a Function5.3. Accepting a Variable Number of Parameters5.4. Accepting Parameters of Any Type5.5. Creating an Anonymous Function5.6. Creating a Function That Maintains State After It Is Called
6. String Recipes
6.0. Introduction6.1. Creating Strings6.2. Converting String to Bytes and Bytes to String6.3. Creating Strings from Other Strings and Data6.4. Converting Strings to Numbers6.5. Converting Numbers to Strings6.6. Replacing Multiple Characters in a String6.7. Creating a Substring from a String6.8. Checking if a String Contains Another String6.9. Splitting a String Into an Array of Strings or Combining an Array of Strings Into a String6.10. Trimming Strings6.11. Capturing String Input from the Command Line6.12. Escaping and Unescaping HTML Strings6.13. Using Regular Expressions
7. General Input/Output Recipes
7.0. Introduction7.1. Reading from an Input7.2. Writing to an Output7.3. Copying from a Reader to a Writer7.4. Reading from a Text File7.5. Writing to a Text File7.6. Using a Temporary File
8. CSV Recipes
8.0. Introduction8.1. Reading the Whole CSV File8.2. Reading a CSV File One Row at a Time8.3. Unmarshalling CSV Data Into Structs8.4. Removing the Header Line8.5. Using Different Delimiters8.6. Ignoring Rows8.7. Writing CSV Files8.8. Writing to File One Row at a Time
9. JSON Recipes
9.0. Introduction9.1. Parsing JSON Data Byte Arrays to Structs9.2. Parsing Unstructured JSON Data9.3. Parsing JSON Data Streams Into Structs9.4. Creating JSON Data Byte Arrays from Structs9.5. Creating JSON Data Streams from Structs9.6. Omitting Fields in Structs

10. Binary Recipes
10.0. Introduction10.1. Encoding Data to gob Format Data10.2. Decoding gob Format Data to Structs10.3. Encoding Data to a Customized Binary Format10.4. Decoding Data with a Customized Binary Format to Structs
11. Date and Time Recipes
11.0. Introduction11.1. Telling Time11.2. Doing Arithmetic with Time11.3. Representing Dates11.4. Representing Time Zones11.5. Representing Duration11.6. Pausing for a Specific Duration11.7. Measuring Lapsed Time11.8. Formatting Time for Display11.9. Parsing Time Displays Into Structs
12. Structs Recipes
12.0. Introduction12.1. Defining Structs12.2. Creating Struct Methods12.3. Creating and Using Interfaces12.4. Creating Struct Instances12.5. Creating One-Time Structs12.6. Composing Structs from Other Structs12.7. Defining Metadata for Struct Fields
13. Data Structure Recipes
13.0. Introduction13.1. Creating Arrays or Slices13.2. Accessing Arrays or Slices13.3. Modifying Arrays or Slices13.4. Making Arrays and Slices Safe for Concurrent Use13.5. Sorting Arrays of Slices13.6. Creating Maps13.7. Accessing Maps13.8. Modifying Maps13.9. Sorting Maps
14. More Data Structure Recipes
14.0. Introduction14.1. Creating Queues14.2. Creating Stacks14.3. Creating Sets14.4. Creating Linked Lists14.5. Creating Heaps14.6. Creating Graphs14.7. Finding the Shortest Path on a Graph
15. Image-Processing Recipes
15.0. Introduction15.1. Loading an Image from a File15.2. Saving an Image to a File15.3. Creating Images15.4. Flipping an Image Upside Down15.5. Converting an Image to Grayscale15.6. Resizing an Image
16. Networking Recipes
16.0. Introduction16.1. Creating a TCP Server16.2. Creating a TCP Client16.3. Creating a UDP Server16.4. Creating a UDP Client
17. Web Recipes
17.0. Introduction17.1. Creating a Simple Web Application17.2. Handling HTTP Requests17.3. Handling HTML Forms17.4. Uploading a File to a Web Application17.5. Serving Static Files17.6. Creating a JSON Web Service API17.7. Serving Through HTTPS17.8. Using Templates for Go Web Applications17.9. Making an HTTP Client Request
18. Testing Recipes
18.0. Introduction18.1. Automating Functional Tests18.2. Running Multiple Test Cases18.3. Setting Up and Tearing Down Before and After Tests18.4. Creating Subtests to Have Finer Control Over Groups of Test Cases18.5. Running Tests in Parallel18.6. Generating Random Test Inputs for Tests18.7. Measuring Test Coverage18.8. Testing a Web Application or a Web Service
19. Benchmarking Recipes
19.0. Introduction19.1. Automating Performance Tests19.2. Running Only Performance Tests19.3. Avoiding Test Fixtures in Performance Tests19.4. Changing the Timing for Running Performance Tests19.5. Running Multiple Performance Test Cases19.6. Comparing Performance Test Results19.7. Profiling a Program
Index
About the Author

Content preview from Go Cookbook

Chapter 7. General Input/Output Recipes

7.0 Introduction

Input and output (more popularly known as I/O) are how a computer communicates with the external world. Typical input into a computer refers to the keystrokes from a keyboard or clicks from or movement of a mouse. It can also refer to other external input sources like a camera or a microphone, gaming joystick, and so on. Output often refers to whatever is shown on the screen (or on the terminal) or printed out on a printer. I/O can also refer to network connections and to files. I/O is a key part of developing software and most programming languages, including Go, have standard libraries that can read from input and write to output.

This chapter explores some common Go recipes for managing I/O. We’ll warm up with some basic I/O recipes, then talk about files in general. In the next few chapters, we’ll move on to CSV, followed by JSON and binary files.

The io package is the base package for input and output in Go and contains interfaces for I/O and a few convenient functions. The main and the most commonly used interfaces are Reader and Writer, but there are several variants of these, like ReadWriter, TeeReader, WriterTo, and many more.

Generally, these interfaces are nothing more than a descriptor for functions. For example, a struct that is a Reader has a Read function. A struct that is a WriterTo has a WriteTo function. Some interfaces combine two or more interfaces. For example, the ReadWriter combines the Reader and ...

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Go Cookbook

by Sau Sheong Chang

Chapter 7. General Input/Output Recipes

7.0 Introduction

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