package main import ( "fmt" "os" ) func main() { file, err := os.Create("message.txt") if err != nil { fmt.Println(err) return } defer file.Close() message := "Hello World!" _, err = file.WriteString(message) if err != nil { fmt.Println(err) return } fmt.Println("Message written successfully to file.") }
package main import ( "fmt" "os" ) func main() { file, err := os.OpenFile("message.txt", os.O_APPEND|os.O_WRONLY, 0644) if err != nil { fmt.Println(err) return } defer file.Close() message := "How are you today?\n" _, err = file.WriteString(message) if err != nil { fmt.Println(err) return } fmt.Println("Message appended successfully to file.") }In this example, we open the existing "message.txt" file in append mode using `os.OpenFile()`. We also specify that we want write-only access to the file. Next, we defer the file's closing to ensure that it is properly closed after we're done using it. We define the message that we want to append to the file and use the `file.WriteString()` function to append it. The function returns the number of bytes written and an error, which we check for and handle accordingly. If there are no errors, we print a success message to the console. Package: os.