feat: add ChannelMerge

channel.go

@@ -2,6 +2,7 @@ package lo
 
 import (
 	"math/rand"
+	"sync"
 	"time"
 )
 
@@ -237,3 +238,28 @@ func BatchWithTimeout[T any](ch <-chan T, size int, timeout time.Duration) (coll
 
 	return buffer, index, time.Since(now), true
 }
+
+// ChannelMerge collect messages from multiple input channels into one buffered channel.
+// output messages has no order guarantee
+func ChannelMerge[T any](channelBufferCap int, upstreams ...<-chan T) <-chan T {
+	out := make(chan T, channelBufferCap)
+	var wg sync.WaitGroup
+
+	// Start an output goroutine for each input channel in upstreams.
+	wg.Add(len(upstreams))
+	for _, c := range upstreams {
+		go func(c <-chan T) {
+			for n := range c {
+				out <- n
+			}
+			wg.Done()
+		}(c)
+	}
+
+	// Start a goroutine to close out once all the output goroutines are done.
+	go func() {
+		wg.Wait()
+		close(out)
+	}()
+	return out
+}

channel_test.go

@@ -302,3 +302,43 @@ func TestBatchWithTimeout(t *testing.T) {
 	is.Equal(0, length5)
 	is.False(ok5)
 }
+
+func TestChannelMerge(t *testing.T) {
+	t.Parallel()
+	testWithTimeout(t, 100*time.Millisecond)
+	is := assert.New(t)
+
+	upstreams := createChannels[int](3, 10)
+	roupstreams := channelsToReadOnly(upstreams)
+	for i := range roupstreams {
+		go func(i int) {
+			upstreams[i] <- 1
+			upstreams[i] <- 1
+			close(upstreams[i])
+		}(i)
+	}
+	out := ChannelMerge(10, roupstreams...)
+	time.Sleep(10 * time.Millisecond)
+
+	// check input channels
+	is.Equal(0, len(roupstreams[0]))
+	is.Equal(0, len(roupstreams[1]))
+	is.Equal(0, len(roupstreams[2]))
+
+	// check channels allocation
+	is.Equal(6, len(out))
+	is.Equal(10, cap(out))
+
+	// check channels content
+	for i := 0; i < 6; i++ {
+		msg0, ok0 := <-out
+		is.Equal(true, ok0)
+		is.Equal(1, msg0)
+	}
+
+	// check it is closed
+	time.Sleep(10 * time.Millisecond)
+	msg0, ok0 := <-out
+	is.Equal(false, ok0)
+	is.Equal(0, msg0)
+}