why wait group faster than channel?

1_wg_example.go

// 1_wg_example.go
package main

import (
    "errors"
    "fmt"
    "sync"
    "time"
)

func doSomething(param string) error {
    time.Sleep(2 * time.Second)
    if param != "ok" {
        return errors.New("an error occurred")
    }
    return nil
}

func main() {
    var wg sync.WaitGroup

    params := []string{"ok", "ok", "b", "c", "ok"}
    var errors []error
    for _, p := range params {
        wg.Add(1)
        fmt.Printf("p %v\n", p)

        go func(p string) {
            defer wg.Done()
            err := doSomething(p)
            if err != nil {
                errors = append(errors, err)
            }
        }(p)
    }
    wg.Wait()

    fmt.Printf("errors %v\n", errors)
}

2_ch_example.go

//2_ch_example.go
package main

import (
    "errors"
    "fmt"
    "time"
)

func doSomething(param string) error {
    time.Sleep(2 * time.Second)
    if param != "ok" {
        return errors.New("an error occurred")
    }
    return nil
}

func main() {
    checkStatus := func(done <-chan interface{}, params ...string) <-chan error {
        errors := make(chan error)
        go func() {
            defer close(errors)
            for _, p := range params {
                fmt.Printf("p %v\n", p)
                err := doSomething(p)
                select {
                case <-done:
                    return
                case errors <- err:
                }
            }
        }()
        return errors
    }

    done := make(chan interface{})
    defer close(done)

    params := []string{"ok", "ok", "b", "c", "ok"}
    for err := range checkStatus(done, params...) {
        fmt.Printf("error %v\n", err)
    }
}

3_result.md

3_result.md

➜  compare-cc time go run wg_example.go
p ok
p ok
p b
p c
p ok
errors [an error occurred an error occurred]
go run wg.go  0.23s user 0.20s system 14% cpu 2.933 total
➜  compare-cc time go run ch_example.go
p ok
p ok
error <nil>
error <nil>
p b
p c
error an error occurred
p ok
error an error occurred
error <nil>
go run ch.go  0.26s user 0.23s system 4% cpu 10.579 total