package main

import (
    "fmt"
    "encoding/json"
)

func main() {
    // Create a map to parse the JSON
    var data map[string]interface{}

    // Define a JSON string
    j := `{"key":"value"}`

    // Parse our JSON string
    err := json.Unmarshal([]byte(j), &data)
    if err != nil {
        fmt.Println("Error parsing JSON string:", err)
    }

    // check if a key exist?
    if  val, ok := data["key"]; ok {
        fmt.Println(val)
    } else {
        fmt.Println("not exist")
    }
}

运行结果：

$ go run e.go
value

参考

https://bencane.com/2020/12/08/maps-vs-structs-for-json/
https://stackoverflow.com/questions/2050391/how-to-check-if-a-map-contains-a-key-in-go