unexpected signal during runtime execution about gmf HOT 3 CLOSED

package snapshot

import (
    "errors"
    "github.com/3d0c/gmf"
    "io/ioutil"
    "os"
)

func Grab(url string) (*os.File, error) {
    inputCtx, err := gmf.NewInputCtx(url)
    if err != nil {
        return nil, err
    }
    defer inputCtx.CloseInputAndRelease()

    srcVideoStream, err := inputCtx.GetBestStream(gmf.AVMEDIA_TYPE_VIDEO)
    if err != nil {
        return nil, err
    }

    codec, err := gmf.FindEncoder("mjpeg")
    if err != nil {
        return nil, err
    }

    cc := gmf.NewCodecCtx(codec)
    defer gmf.Release(cc)
    cc.SetPixFmt(gmf.AV_PIX_FMT_YUVJ420P)
    cc.SetWidth(srcVideoStream.CodecCtx().Width())
    cc.SetHeight(srcVideoStream.CodecCtx().Height())
    cc.SetTimeBase(srcVideoStream.CodecCtx().TimeBase().AVR())

    if codec.IsExperimental() {
        cc.SetStrictCompliance(gmf.FF_COMPLIANCE_EXPERIMENTAL)
    }

    if err := cc.Open(nil); err != nil {
        return nil, err
    }

    for packet := range inputCtx.GetNewPackets() {
        if packet.StreamIndex() != srcVideoStream.Index() {
            continue
        }

        ist, err := inputCtx.GetStream(packet.StreamIndex())
        if err != nil {
            return nil, err
        }
        for frame := range packet.Frames(ist.CodecCtx()) {
            if p, ready, _ := frame.EncodeNewPacket(cc); ready {
                defer gmf.Release(p)
                return newFile(p.Data())
            }
        }
    }
    return nil, errors.New("can not get Packets")
}

func newFile(b []byte) (*os.File, error) {
    fp, err := ioutil.TempFile("", "snapshot_")
    if err != nil {
        return nil, err
    }
    defer fp.Close()
    _, err = fp.Write(b)
    if err != nil {
        return nil, err
    } else {
        return fp, nil
    }
}

package main

import (
    "errors"
    "io/ioutil"
    "log"
    "os"
    "sync"

    "github.com/3d0c/gmf"
)

func Grab(url string, wg *sync.WaitGroup) (*os.File, error) {
    defer wg.Done()

    inputCtx, err := gmf.NewInputCtx(url)
    if err != nil {
        return nil, err
    }
    defer inputCtx.CloseInputAndRelease()

    srcVideoStream, err := inputCtx.GetBestStream(gmf.AVMEDIA_TYPE_VIDEO)
    if err != nil {
        return nil, err
    }

    codec, err := gmf.FindEncoder("mjpeg")
    if err != nil {
        return nil, err
    }

    cc := gmf.NewCodecCtx(codec)
    defer gmf.Release(cc)
    cc.SetPixFmt(gmf.AV_PIX_FMT_YUVJ420P)
    cc.SetWidth(srcVideoStream.CodecCtx().Width())
    cc.SetHeight(srcVideoStream.CodecCtx().Height())
    cc.SetTimeBase(srcVideoStream.CodecCtx().TimeBase().AVR())

    if codec.IsExperimental() {
        cc.SetStrictCompliance(gmf.FF_COMPLIANCE_EXPERIMENTAL)
    }

    if err := cc.Open(nil); err != nil {
        return nil, err
    }

    for packet := range inputCtx.GetNewPackets() {
        if packet.StreamIndex() != srcVideoStream.Index() {
            continue
        }

        ist, err := inputCtx.GetStream(packet.StreamIndex())
        if err != nil {
            return nil, err
        }
        for frame := range packet.Frames(ist.CodecCtx()) {
            if p, ready, _ := frame.EncodeNewPacket(cc); ready {
                defer gmf.Release(p)
                return newFile(p.Data())
            }
        }
    }
    return nil, errors.New("can not get Packets")
}

func newFile(b []byte) (*os.File, error) {
    log.Println("len(b):", len(b))
    fp, err := ioutil.TempFile("./", "snapshot_")
    if err != nil {
        return nil, err
    }
    defer fp.Close()

    n, err := fp.Write(b)
    log.Println(n, "written to", fp.Name())

    if err != nil {
        return nil, err
    } else {
        return fp, nil
    }
}

func main() {
    // runtime.GOMAXPROCS(runtime.NumCPU())

    src := []string{"tmp/vid480.mp4", "tmp/vid481.mp4", "tmp/vid482.mp4", "tmp/vid483.mp4", "tmp/vid484.mp4", "tmp/vid485.mp4"}

    wg := new(sync.WaitGroup)

    for _, url := range src {
        wg.Add(1)
        go func(url string) {
            fp, err := Grab(url, wg)
            log.Println(fp, err)
        }(url)
    }

    wg.Wait()
}