go error monad

error.go

package main

import (
    "errors"
    "log"
)

type F func() error

func errCompose(pipeline ...F) (e error, ok bool) {
    ok = true

    for _, f := range pipeline {
        e = f()

        if e != nil {
            ok = false
            break
        }
    }

    return
}

func main() {
    good := func() error {
        log.Println("good function called")
        return nil
    }

    good2 := func() error {
        log.Println("good function 2 called")
        return nil
    }

    bad := func() error {
        log.Println("bad function called")
        return errors.New("bad function returned error")
    }

    // if pipeline succeeds, handler does not get called
    if _, ok := errCompose(good, good, good); !ok {
        log.Println("this shouldn't happen")
    }

    // pipeline interrupts at first error
    if e, ok := errCompose(good, bad, good2); !ok {
        log.Println("good2 was not called:", e)
    }
}