Golang with JSON

1. Read from Json file and convert to struct

   type Record struct {
   	Time        time.Time
   	Station     string
   	Temperature float64
   	Rain        float64
   }
   
   func readRecord(fileName string) (Record, error) {
   	file, err := os.Open(fileName)
   	if err != nil {
   		log.Fatal(err)
   	}
   	defer file.Close()
   	var rec Record
   	dec := json.NewDecoder(file)
   	if err := dec.Decode(&rec); err != nil {
   		return Record{}, err
   	}
   	return rec, nil
   }
   func main() {
   	fileName := "sample-app/record.json"
   	rec, err := readRecord(fileName)
   	if err != nil {
   		log.Fatal(err)
   	}
   	fmt.Printf("%+v\n", rec)
   }
   

2. Convert Json string to stuct

   type Student struct {
   	Name string // The name must start with upper case
   	Age  int
   }
   jsonTxt := `[{"name":"tom", "age":13},{"name":"Lily", "age":14}]`
   	var students []Student
   	json.Unmarshal([]byte(jsonTxt), &students)
   	for _, stu := range students {
   		fmt.Printf("%+v", stu)
   	}
   

3. Convert Map to Json text

func main() {
	states := make(map[string]string)
	states["WA"] = "Washington"
	states["NY"] = "New York"
	states["CA"] = "California"
	jsonText, _ := json.Marshal(states)
	fmt.Println(string(jsonText))
}