Why don't I see fmt logs in my terminal when running go app locally?-CodePudding

I'm trying to debug my golang app. Currently, I have an API request that isn't working which has this line of code: fmt.Errorf("Object(%q).CopierFrom(%q).Run: %v", dstName, object, err)

How can I view the output of this error log? And if it's not possible what are some other ways to debug in go? (runtime invocation would be nice)

CodePudding user response：

fmt.Errorf() creates an error object. but not print.doc

If you're just trying to print the message to stdout: run

package main

import (
    "fmt"
)

func main() {
    const name, id = "bueller", 17
    err := fmt.Errorf("user %q (id %d) not found", name, id)
    fmt.Println(err.Error())

}

out:

user "bueller" (id 17) not found

if you want debug golang code, I recommend use log packages for example: zerolog


package main

import (
    "errors"

    "github.com/rs/zerolog"
    "github.com/rs/zerolog/log"
)

func main() {
    // UNIX Time is faster and smaller than most timestamps
    zerolog.TimeFieldFormat = zerolog.TimeFormatUnix

    err := errors.New("seems we have an error here")
    log.Error().Err(err).Msg("this is an error")
}

out:

{"level":"error","error":"seems we have an error here","time":1640795128,"message":"this is an error"}

CodePudding user response：

fmt.Errorf creates an error - ideal for function returns - but it's not implicitly logged.

If you want to log an error simply:

log.Printf("api X: error %v", err)

CodePudding user response：

fmt.Errorf creates an error object; it does not print.

From the docs for fmt.Errorf:

func Errorf(format string, a ...interface{}) error

If you're just trying to print the message to stdout:

fmt.Printf("Object(%q).CopierFrom(%q).Run: %v\n", dstName, object, err)

If you want to write to an error log, I recommend looking at the log package. For example, if you were looking to write to stderr:

logger := log.New(os.Stderr, "my-app", 0)
logger.Printf("Object(%q).CopierFrom(%q).Run: %v", dstName, object, err)