Book Image

The Go Workshop

By : Delio D'Anna, Andrew Hayes, Sam Hennessy, Jeremy Leasor, Gobin Sougrakpam, Dániel Szabó
Book Image

The Go Workshop

By: Delio D'Anna, Andrew Hayes, Sam Hennessy, Jeremy Leasor, Gobin Sougrakpam, Dániel Szabó

Overview of this book

The Go Workshop will take the pain out of learning the Go programming language (also known as Golang). It is designed to teach you to be productive in building real-world software. Presented in an engaging, hands-on way, this book focuses on the features of Go that are used by professionals in their everyday work. Each concept is broken down, clearly explained, and followed up with activities to test your knowledge and build your practical skills. Your first steps will involve mastering Go syntax, working with variables and operators, and using core and complex types to hold data. Moving ahead, you will build your understanding of programming logic and implement Go algorithms to construct useful functions. As you progress, you'll discover how to handle errors, debug code to troubleshoot your applications, and implement polymorphism using interfaces. The later chapters will then teach you how to manage files, connect to a database, work with HTTP servers and REST APIs, and make use of concurrent programming. Throughout this Workshop, you'll work on a series of mini projects, including a shopping cart, a loan calculator, a working hours tracker, a web page counter, a code checker, and a user authentication system. By the end of this book, you'll have the knowledge and confidence to tackle your own ambitious projects with Go.

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Table of Contents (21 chapters)
Preface
Preface
About the Book
Free Chapter
1
1. Variables and Operators
1. Variables and Operators
Introduction
Summary
2
2. Logic and Loops
2. Logic and Loops
Introduction
Summary
3
3. Core Types
3. Core Types
Introduction
True and False
Numbers
Byte
Text
The nil Value
Summary
4
4. Complex Types
4. Complex Types
Introduction
Collection Types
Arrays
Slice
Simple Custom Types
Structs
Summary
5
5. Functions
5. Functions
Introduction
Functions
fizzBuzz
Parameters
Naked Returns
Closures
defer
Summary
6
6. Errors
6. Errors
Introduction
What Are Errors?
Error Handling Using Other Programming Languages
Error Interface Type
Panic
Recover
Summary
7
7. Interfaces
7. Interfaces
Introduction
Interface
Duck Typing
Polymorphism
Accepting Interfaces and Returning Structs
Summary
8
8. Packages
8. Packages
Introduction
What Is a Package?
Exported and Unexported Code
The init() Function
Summary
9
9. Basic Debugging
9. Basic Debugging
Introduction
Methods for Bug-Free Code
Basic Debugging
Logging
Log Fatal Errors
Summary
10
10. About Time
10. About Time
Introduction
Making Time
Comparing Time
Duration Calculation
Managing Time
Formatting Time
Summary
11
11. Encoding and Decoding (JSON)
11. Encoding and Decoding (JSON)
Introduction
JSON
Decoding JSON
Encoding JSON
GOB: Go's Own Encoding
Summary
12
12. Files and Systems
12. Files and Systems
Introduction
Filesystem
Flags and Arguments
Creating and Writing to Files
CSV
Summary
13
13. SQL and Databases
13. SQL and Databases
Introduction
The Database
Database API and Drivers
Connecting to Databases
Creating Tables
Inserting Data
Retrieving Data
Updating Existing Data
Deleting Data
Truncating and Deleting Table
Summary
14
14. Using the Go HTTP Client
14. Using the Go HTTP Client
Introduction
The Go HTTP Client and Its Uses
Sending a Request to a Server
Structured Data
Sending Data to a Server
Summary
15
15. HTTP Servers
15. HTTP Servers
Introduction
How to Build a Basic Server
HTTP Handler
Simple Routing
Handler versus Handler Function
Returning Complex Structures
Dynamic Content
Templating
Static Resources
Getting Some Style
Getting Dynamic
HTTP Methods
JSON loads
Summary
16
16. Concurrent Work
16. Concurrent Work
Introduction
Goroutines
WaitGroup
Race Conditions
Atomic Operations
Invisible Concurrency
Channels
The Importance of Concurrency
Concurrency Patterns
Buffers
HTTP Servers
Methods as Routines
Go Context Package
Summary
17
17. Using Go Tools
17. Using Go Tools
Introduction
The go build Tool
The go run Tool
The gofmt Tool
The goimports Tool
The go vet Tool
The Go Race Detector
The go doc Tool
The go get Tool
Summary
18
18. Security
18. Security
Introduction
Application Security
Cross-Site Scripting
Cryptography
Encryption
Random Generators
HTTPS/TLS
Password Management
Summary
19
19. Special Features
19. Special Features
Introduction
Build Constraints
Reflection
TypeOf and ValueOf
DeepEqual
Wildcard Pattern
The unsafe Package
Summary
Appendix
Appendix
1. Variables and Operators
2. Logic and Loops
3. Core Types
4. Complex Types
5. Functions
6. Errors
7. Interfaces
8. Packages
9. Basic Debugging
10. About Time
11. Encoding and Decoding (JSON)
12. Files and Systems
13. SQL and Databases
14. Using the Go HTTP Client
15. HTTP Servers
16. Concurrent Work
17. Using Go Tools
18. Security
19. Special Features
What Next?

Inserting Data

Long ago, when the era of web applications backed by SQL databases started to bloom, there were some gutsy people who invented the SQL injection attack. A type of authentication is done via SQL queries against a database and, for example, after converting the password with mathematical magic into hash functions, all the web app did was execute the query with the username and password coming from the input of the form. Many servers executed something like this:

"SELECT password FROM Auth WHERE username=<input from user>"

Then, the password gets rehashed; if the two hashes match, the password was good for the user.

The problem with this came from the <input from user> part, because if the attacker was smart enough, they could reformulate the query and run additional commands. For example:

"SELECT password FROM Auth WHERE username=<input  from user> OR '1'='1'"

The problem with this query is that OR...

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