How do I handle plain text HTTP Get response in Golang?

With io.Copy you read all bytes from an io.Reader, and write it to an io.Writer

resp, err := http.Get(server.URL + "/v1/ping")
if err != nil {
    t.Errorf("failed to execute GET request: %s", err)
}
defer resp.Body.Close()

var b bytes.Buffer
if _, err := io.Copy(&b, resp.Body); err != nil {
    t.Errorf("failed to copy response body: %s", err)
}

fmt.Println(b.String())

Response of the body can be read using any method that could read data from incoming byte stream. Simplest of them is ReadAll function provided in ioutil package.

responseData,err := ioutil.ReadAll(response.Body)
if err != nil {
    log.Fatal(err)
}

It will give you API response in []byte. If response is plain text you can easily convert it into string using type conversion:

responseString := string(responseData)

And Check the result

fmt.Println(responseString)

Sample Program:

package main

import (
    "fmt"
    "io/ioutil"
    "log"
    "net/http"
)

func main() {
    url := "http://country.io/capital.json"
    response, err := http.Get(url)
    if err != nil {
        log.Fatal(err)
    }
    defer response.Body.Close()

    responseData, err := ioutil.ReadAll(response.Body)
    if err != nil {
        log.Fatal(err)
    }

    responseString := string(responseData)

    fmt.Println(responseString)
}

Use ioutil.ReadAll(response.Body).

Also you may handle Unicode text using bufio.NewScanner(response.Body)
like this working sample code:

package main

import (
    "bufio"
    "bytes"
    "fmt"
    "log"
    "net/http"
)

func main() {
    response, err := http.Get("http://127.0.0.1")
    if err != nil {
        log.Fatal(err)
    }
    defer response.Body.Close()

    scanner := bufio.NewScanner(response.Body)
    scanner.Split(bufio.ScanRunes)
    var buf bytes.Buffer
    for scanner.Scan() {
        buf.WriteString(scanner.Text())
    }
    fmt.Println(buf.String())
}

output:

*Hello World* B=µH *

Using this sample web server code:

package main

import (
    "fmt"
    "log"
    "net/http"
)

func ServeHTTP(w http.ResponseWriter, r *http.Request) {
    body := "*Hello World* B=µH *"
    fmt.Fprint(w, body)
}

func main() {
    http.HandleFunc("/", ServeHTTP)
    if err := http.ListenAndServe(":80", nil); err != nil {
        log.Fatal(err)
    }
}