Mastering Go - Second Edition

Printing line numbers in log entries

In this section, you are going to learn how to print the line number of the source file that executed the statement that wrote the log entry to a log file using the Go code of customLogLineNumber.go. This will be presented in two parts. The first part is as follows:

package main 
 
import ( 
    "fmt" 
    "log" 
    "os" 
) 
 
var LOGFILE = "/tmp/mGo.log" 
 
func main() { 
    f, err := os.OpenFile(LOGFILE, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644) 
 
    if err != nil { 
        fmt.Println(err) 
        return 
    } 
    defer f.Close() 

So far, there is nothing special when compared to the code of customLog.go.

The remaining Go code of customLogLineNumber.go is as follows:

 iLog := log.New(f, "customLogLineNumber ", log.LstdFlags) iLog.SetFlags(log.LstdFlags ...