GoLang Tutorial - JSON

JSON (JavaScript Object Notation) is a simple data interchange format. It is most commonly used for communication between web back-ends and JavaScript programs running in the browser, but it is used in many other places, too.

With the json package it's a snap to read and write JSON data from our Go programs.

func Marshal(v interface{}) ([]byte, error)

The function returns the JSON encoding form of v.

With a given Go data structure, Message:

type Message struct {
    Name string
    Body string
    Time int64
}

and an instance of Message

m := Message{"Interface", "Empty Interface", 1556747623}

We can marshal a JSON-encoded version of m using json.Marshal:

b, err := json.Marshal(m)

If all is well, err will be nil and b will be a []byte containing this JSON data:

b == []byte(`{"Name":"Interface","Body":"Empty Interface","Time":1556747623}`)

Here is the full code:

The code: json-marshall.go

To decode JSON data we use the Unmarshal() function:

func Unmarshal(data []byte, v interface{}) error

We must first create a place where the decoded data will be stored:

var m Message

and call json.Unmarshal, passing it a []byte of JSON data and a pointer to m:

err := json.Unmarshal(b, &m)

If b contains valid JSON that fits in m, after the call err will be nil and the data from b will have been stored in the struct m, as if by an assignment like:

m = Message{
    Name: "Interface",
    Body: "Empty Interface",
    Time: 1556747623,
}

Here is the full code:

The code: json-unmarshall.go

Go Tutorial

1. GoLang Tutorial - HelloWorld
2. Calling code in an external package & go.mod / go.sum files
3. Workspaces
4. Workspaces II
5. Visual Studio Code
6. Data Types and Variables
7. byte and rune
8. Packages
9. Functions
10. Arrays and Slices
11. A function taking and returning a slice
12. Conditionals
13. Loops
14. Maps
15. Range
16. Pointers
17. Closures and Anonymous Functions
18. Structs and receiver methods
19. Value or Pointer Receivers
20. Interfaces
21. Web Application Part 0 (Introduction)
22. Web Application Part 1 (Basic)
23. Web Application Part 2 (Using net/http)
24. Web Application Part 3 (Adding "edit" capability)
25. Web Application Part 4 (Handling non-existent pages and saving pages)
26. Web Application Part 5 (Error handling and template caching)
27. Web Application Part 6 (Validating the title with a regular expression)
28. Web Application Part 7 (Function Literals and Closures)
29. Building Docker image and deploying Go application to a Kubernetes cluster (minikube)
30. Serverless Framework (Serverless Application Model-SAM)
31. Serverless Web API with AWS Lambda
32. Arrays vs Slices with an array left rotation sample
33. Variadic Functions
34. Goroutines
35. Channels ("<-")
36. Channels ("<-") with Select
37. Channels ("<-") with worker pools
38. Defer
39. GoLang Panic and Recover
40. String Formatting
41. JSON
42. SQLite
43. Modules 0: Using External Go Modules from GitHub
44. Modules 1 (Creating a new module)
45. Modules 2 (Adding Dependencies)
46. AWS SDK for Go (S3 listing)
47. Linked List
48. Binary Search Tree (BST) Part 1 (Tree/Node structs with insert and print functions)
49. Go Application Authentication I (BasicAuth, Bearer-Token-Based Authentication)
50. Go Application Authentication II (JWT Authentication)