How to handle required command-line flags and error handling in Go?

In Go, command-line flags can be easily handled using the flag package provided by the standard library. To handle required flags and error handling, you can follow these steps:

Import the flag and fmt packages:

import (
    "flag"
    "fmt"
)

Define the required flags using the flag package:

var (
    requiredFlag = flag.String("requiredFlag", "", "Description of the required flag")
)

Here, requiredFlag is the name of the required flag, "" is the default value, and the string is the description of the flag.

Implement a function to check if required flags are set:

func areRequiredFlagsSet() bool {
    if *requiredFlag == "" {
        return false
    }
    return true
}

This function checks if the required flag value is empty or not.

Parse the command-line arguments:

flag.Parse()

This code parses the command-line arguments provided to the program.

Check and handle errors:

if !areRequiredFlagsSet() {
    fmt.Println("Required flags are missing.")
    flag.PrintDefaults()
    return
}

If the required flags are not set, it will print an error message along with the default flag values and exit the program.

Now you can use the value of the required flag anywhere in your program by accessing the *requiredFlag variable.

Remember to call flag.Parse() before accessing the flag value.

Additionally, you can define other optional flags using the same method, and the flag package will handle all the parsing and default values for you.