Golang: Http Get Request example

Go standard library comes with "net/http" package which has excellent support for  HTTP Client and Server.  

In this example we will be using "http.Get" method to execute Http Get method. We will convert the response to String and print it.

package main

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

func main(){

	//Use get method to hit the rest API
	resp, err := http.Get("https://reqres.in/api/users/2")

	// An error is returned if there were too many redirects
	// or if there was an HTTP protocol error
	if err != nil {
		panic(err)
	}
	//Need to close the response stream, once response is read.
	//Hence defer close. It will automatically take care of it.
	defer resp.Body.Close()

	//Check response code, if ok then read response.
	if resp.StatusCode == http.StatusOK {
		body, err := ioutil.ReadAll(resp.Body)
		if err != nil {
			//Failed to read response.
			panic(err)
		}

		//Convert bytes to String and print
		jsonStr := string(body)
		fmt.Println("Response: ", jsonStr)

	} else {
		//The status is not ok. print the error.
		fmt.Println("Get failed with error: ", resp.Status)
	}
}

Its simple and easy to implement.

Golang: Reading environment variables

Usually, environment variables are used to provide the configuration information for the program. You can set the environment outside of the program and you can assess these during execution. Go provides the simplest mechanism to access the environment variables. 

You can use 'OS' package to get or set the environment variables.

package main

import (
	"fmt"
	"os"
	"strings"
)

func main() {
	//Read single environment variable value
	val := os.Getenv("WORKING_DIR")
	//Check if the value is set.
	if val != "" {
		fmt.Println("Working Dir is: ", val )
	} else {
		fmt.Println("Working Dir is not set. Setting it now.")
		//You can set env variable using setEnv method.
		os.Setenv("WORKING_DIR", "/root/app_dir")
		fmt.Println("Working Dir is: ", os.Getenv("WORKING_DIR") )
	}

	//You can also iterate over all the environment variables.
	//Here environment variables are returned as string containing varname=value form
	for _, varNVal := range os.Environ() {
		keyVal := strings.SplitN(varNVal, "=", 2)
		fmt.Println("Variable name: " + keyVal[0] + "\tValue: " + keyVal[1] )
	}
}

Golang: Write data to file

Writing data to file is the most common use case while writing a program.  Here we are going to see multiple ways of writing data to file.  

Write using ioutil.WriteFile

You can directly write data to file using ioutil.WriteFile" method. It will take care of creating file if the file does not exists.

package main

import (
	"fmt"
	"io/ioutil"
)

func main() {
	writeStringToFile("data.txt", "Hello File!!!")
}

func writeStringToFile(filePath string, data string) {

	//Need to convert string to byte array.
	//WriteFile will create and write data to file, if file does not exists.
	err := ioutil.WriteFile(filePath, []byte(data), 0644)
	checkNLogError(err)
}

func checkNLogError(err error){
	if err != nil {
		fmt.Println(err)
                panic(err)
	}
}

Write using WriteString

You need to create a file first, using the same file pointer we can write string to file.

package main

import (
	"fmt"
	"os"
)

func main() {
	writeStringToFile("data.txt", "Hello File!!!")
}

func writeStringToFile(filePath string, data string) {

	//Create a file to write data.
	f, err := os.Create(filePath)

	//If there is error to write to file, exit.
	checkNLogError(err)

	//Once file is opened, it should be closed.
	//Defer will take care of it, even if any error.
	defer f.Close()

	//Write data to file.
	_, err2 := f.WriteString(data)

	//Check if there is any error during writing data to file.
	checkNLogError(err2)
}

func checkNLogError(err error){
	if err != nil {
		fmt.Println(err)
		panic(err)
	}
}