Golang HTTP Request returning 200 response but empty body

Question

I'm doing a post request and I get a 200 OK response. I also receive the headers. However, the body keeps coming back empty. There should be a body, when I run it in postman the body shows up. What am I missing here?

func AddHealthCheck(baseURL string, payload HealthCheck, platform string, hostname string) (string, error) {
    url := fmt.Sprintf(baseURL+"add-healthcheck/%s/%s", platform, hostname)

    //convert go struct to json
    jsonPayload, err := json.Marshal(payload)
    if err != nil {
        log.Error("[ADD HEALTH CHECK] Could not convert go struct to json : ", err)
        return "", err
    }

    // Create client & set timeout
    client := &http.Client{}
    client.Timeout = time.Second * 15

    // Create request
    req, err := http.NewRequest("POST", url, bytes.NewBuffer(jsonPayload))
    if err != nil {
        log.Error("[ADD HEALTH CHECK] Could not create request : ", err)
        return "", err
    }
    req.Header.Set("Content-Type", "application/json")

    // Fetch Request
    resp, err := client.Do(req)
    if err != nil {
        log.Error("[ADD HEALTH CHECK] Could not fetch request : ", err)
        return "", err
    }
    defer resp.Body.Close()

    // Read Response Body
    respBody, err := ioutil.ReadAll(resp.Body)
    if err != nil {
        log.Error("[HEALTH CHECK] Could not read response body : ", err)
        return "", err
    }

    fmt.Println("response Status : ", resp.Status)
    fmt.Println("response Headers : ", resp.Header)
    fmt.Println("response Body : ", string(respBody))

    return string(respBody), nil
}

Solution

I have confirmed locally that your code, as shown, should work.

Here is the code I used:

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "io/ioutil"
    "net/http"
    "time"
)

func main() {
    http.HandleFunc("/", handler)
    go func(){
        http.ListenAndServe(":8080", nil)
    }()

    AddHealthCheck()
}

func handler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hi there")
}

func panicError(err error) {
    if err != nil {
        panic(err)
    }
}

func AddHealthCheck() (string, error) {

    //convert go struct to json
    payload := "bob"
    jsonPayload, err := json.Marshal(payload)
    panicError(err)

    // Create client & set timeout
    client := &http.Client{}
    client.Timeout = time.Second * 15

    // Create request
    req, err := http.NewRequest("POST", "http://localhost:8080", bytes.NewBuffer(jsonPayload))
    panicError(err)
    req.Header.Set("Content-Type", "application/json")

    // Fetch Request
    resp, err := client.Do(req)
    panicError(err)
    defer resp.Body.Close()

    // Read Response Body
    respBody, err := ioutil.ReadAll(resp.Body)
    panicError(err)

    fmt.Println("response Status : ", resp.Status)
    fmt.Println("response Headers : ", resp.Header)
    fmt.Println("response Body : ", string(respBody))

    return string(respBody), nil
}

The code above is just a slightly stripped down version of your code, and it outputs the body of the response. (Note that I provide a server here to receive the post request and return a response)

The server is simply not sending you a body. You can confirm this with something like wireshark.

If you are getting a body back using postman, you must be sending a different request in postman than in go. It can sometimes be tough to see what is the difference, as both go and postman can sometimes add headers behind the scenes that you don't see. Again, something like wireshark can help here.

Or if you have access to the server, you can add logs there.