为什么Go json.Marshal拒绝这些struct标签？ json标签的正确语法是什么？ [重复]

Question

This question already has an answer here:

• Can't unmarshall JSON with key names having spaces 1 answer

I am trying to use json.Marshal but it refuses to accept my struct tags.

What am I doing wrong?

Here is the source code for "marshal.go"

https://play.golang.org/p/eFe03_89Ly9

package main

import (
    "encoding/json"
    "fmt"
)

type Person struct {
    Name string `json: "name"`
    Age  int    `json: "age"`
}

func main() {
    p := Person{Name: "Alice", Age: 29}
    bytes, _ := json.Marshal(p)
    fmt.Println("JSON = ", string(bytes))
}

I get these error messages from "go vet marshal.go"

./marshal.go:9: struct field tag `json: "name"` not compatible with reflect.StructTag.Get: bad syntax for struct tag value
./marshal.go:10: struct field tag `json: "age"` not compatible with reflect.StructTag.Get: bad syntax for struct tag value

I get this output when I run the program.

% ./marshal
JSON =  {"Name":"Alice","Age":29}

Notice the field names match the Go structure and ignore the json tags.

What am I missing?

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Answer 1

Oh my goodness! I just figured it out. There is no space allowed between json: and the field name "name".

The "go vet" error message ("bad syntax") is remarkably unhelpful.

The following code works. Can you see the difference?

package main

import (
    "encoding/json"
    "fmt"
)

type Person struct {
    Name string `json:"name"`
    Age  int    `json:"age"`
}

func main() {
    p := Person{Name: "Alice", Age: 29}
    bytes, _ := json.Marshal(p)
    fmt.Println("JSON = ", string(bytes))
}