How Can I Get the Line Number of Errors in My Go Code?

Retrieving the Line Number of Errors in Golang

When you encounter errors in your Golang code, logging them for debugging purposes is crucial. However, log.Fatal alone does not provide the line number where the error occurred. This can make tracing the source of the error difficult.

To address this issue, you can modify the log flags to include line number information. Here's how:

• Custom Logger: You can create a custom logger and set its Flags field to include the desired line number format (Llongfile for full path, Lshortfile for just the file name).

myLogger := log.New(os.Stdout, "", log.LstdFlags|log.Lshortfile)

• Default Logger: you can also modify the Flags of the default logger to include the line number information:

log.SetFlags(log.LstdFlags | log.Lshortfile)

By setting these flags, the log output will now include the line of offending code:

import (
    "log"
)

func main() {
    log.SetFlags(log.LstdFlags | log.Lshortfile)
    log.Fatal("Error occurred on line 14 in file my_file.go")
}

Output:

2022/09/20 13:52:15 my_file.go:14: Error occurred on line 14 in file my_file.go

This provides a more detailed error message, making it easier to identify and fix the underlying issue. Note that this method prints the line number only in case of fatal errors (e.g., log.Fatal). For other log levels (e.g., log.Error), you can use debug.PrintStack() to print the full call stack.

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