你需要从req.Body中读取。ParseForm方法正在从请求中读取数据。主体，然后以标准HTTP编码格式解析它。您需要的是读取正文并以JSON格式解析它。

这是更新后的代码。

package main

import (
    "encoding/json"
    "log"
    "net/http"
    "io/ioutil"
)

type test_struct struct {
    Test string
}

func test(rw http.ResponseWriter, req *http.Request) {
    body, err := ioutil.ReadAll(req.Body)
    if err != nil {
        panic(err)
    }
    log.Println(string(body))
    var t test_struct
    err = json.Unmarshal(body, &t)
    if err != nil {
        panic(err)
    }
    log.Println(t.Test)
}

func main() {
    http.HandleFunc("/test", test)
    log.Fatal(http.ListenAndServe(":8082", nil))
}

请使用json。解码器而不是json.Unmarshal。

func test(rw http.ResponseWriter, req *http.Request) {
    decoder := json.NewDecoder(req.Body)
    var t test_struct
    err := decoder.Decode(&t)
    if err != nil {
        panic(err)
    }
    log.Println(t.Test)
}

我发现下面的文档示例非常有用。

package main

import (
    "encoding/json"
    "fmt"
    "io"
    "log"
    "strings"
)

func main() {
    const jsonStream = `
        {"Name": "Ed", "Text": "Knock knock."}
        {"Name": "Sam", "Text": "Who's there?"}
        {"Name": "Ed", "Text": "Go fmt."}
        {"Name": "Sam", "Text": "Go fmt who?"}
        {"Name": "Ed", "Text": "Go fmt yourself!"}
    `
    type Message struct {
        Name, Text string
    }
    dec := json.NewDecoder(strings.NewReader(jsonStream))
    for {
        var m Message
        if err := dec.Decode(&m); err == io.EOF {
            break
        } else if err != nil {
            log.Fatal(err)
        }
        fmt.Printf("%s: %s\n", m.Name, m.Text)
    }
}

这里的关键是操作人员想要解码

type test_struct struct {
    Test string
}

.．.在这种情况下，我们将删除const jsonStream，并将Message结构体替换为test_struct:

func test(rw http.ResponseWriter, req *http.Request) {
    dec := json.NewDecoder(req.Body)
    for {
        var t test_struct
        if err := dec.Decode(&t); err == io.EOF {
            break
        } else if err != nil {
            log.Fatal(err)
        }
        log.Printf("%s\n", t.Test)
    }
}

更新:我还想补充一点，这篇文章提供了一些关于使用JSON响应的很棒的数据。作者解释了结构标签，我不知道。

因为JSON通常看起来不像{"Test": "Test"， "SomeKey": "SomeVal"}，而是{"Test": "Test"， "SomeKey": "some value"}，你可以像这样重构你的结构:

type test_struct struct {
    Test string `json:"test"`
    SomeKey string `json:"some-key"`
}

.．.现在你的处理程序将使用“some-key”来解析JSON，而不是“SomeKey”(你将在内部使用)。

这个问题快把我逼疯了。我的JSON编组器和解组器没有填充我的Go结构。然后我在https://eager.io/blog/go-and-json:上找到了解决方案

与Go中的所有结构体一样，重要的是只记住这一点 首字母大写的字段对外部程序可见 比如JSON编组器。”

在那之后，我的Marshaller和Unmarshaller工作得很完美!

为什么要使用json有两个原因。解码器应该优先于json。Unmarshal——2013年最流行的答案中没有提到:

February 2018, go 1.10 introduced a new method json.Decoder.DisallowUnknownFields() which addresses the concern of detecting unwanted JSON-input req.Body is already an io.Reader. Reading its entire contents and then performing json.Unmarshal wastes resources if the stream was, say a 10MB block of invalid JSON. Parsing the request body, with json.Decoder, as it streams in would trigger an early parse error if invalid JSON was encountered. Processing I/O streams in realtime is the preferred go-way.

处理一些关于检测错误用户输入的用户评论:

要执行强制字段和其他卫生检查，请尝试:

d := json.NewDecoder(req.Body)
d.DisallowUnknownFields() // catch unwanted fields

// anonymous struct type: handy for one-time use
t := struct {
    Test *string `json:"test"` // pointer so we can test for field absence
}{}

err := d.Decode(&t)
if err != nil {
    // bad JSON or unrecognized json field
    http.Error(rw, err.Error(), http.StatusBadRequest)
    return
}

if t.Test == nil {
    http.Error(rw, "missing field 'test' from JSON object", http.StatusBadRequest)
    return
}

// optional extra check
if d.More() {
    http.Error(rw, "extraneous data after JSON object", http.StatusBadRequest)
    return
}

// got the input we expected: no more, no less
log.Println(*t.Test)

操场上

典型的输出:

$ curl -X POST -d "{}" http://localhost:8082/strict_test

expected json field 'test'

$ curl -X POST -d "{\"Test\":\"maybe?\",\"Unwanted\":\"1\"}" http://localhost:8082/strict_test

json: unknown field "Unwanted"

$ curl -X POST -d "{\"Test\":\"oops\"}g4rB4g3@#$%^&*" http://localhost:8082/strict_test

extraneous data after JSON

$ curl -X POST -d "{\"Test\":\"Works\"}" http://localhost:8082/strict_test 

log: 2019/03/07 16:03:13 Works

type test struct {
    Test string `json:"test"`
}

func test(w http.ResponseWriter, req *http.Request) {
    var t test_struct

    body, _ := ioutil.ReadAll(req.Body)
    json.Unmarshal(body, &t)

    fmt.Println(t)
}

我喜欢在本地定义自定义结构。所以:

// my handler func
func addImage(w http.ResponseWriter, r *http.Request) {

    // define custom type
    type Input struct {
        Url        string  `json:"url"`
        Name       string  `json:"name"`
        Priority   int8    `json:"priority"`
    }

    // define a var 
    var input Input

    // decode input or return error
    err := json.NewDecoder(r.Body).Decode(&input)
    if err != nil {
        w.WriteHeader(400)
        fmt.Fprintf(w, "Decode error! please check your JSON formating.")
        return
    }

    // print user inputs
    fmt.Fprintf(w, "Inputed name: %s", input.Name)

}