generics to fight boilerplate

nine.diff

diff --git a/main.go b/main.go
index b850a16..6745855 100644
--- a/main.go
+++ b/main.go
@@ -121,7 +121,7 @@ func main() {
 		errors = append(errors, lowerCaseErrors)
 	}
 
-	stage1Merged := mergeStringChans(ctx, stage1Channels...)
+	stage1Merged := mergeChans(ctx, stage1Channels...)
 	stage2Channels := []<-chan string{}
 
 	for i := 0; i < runtime.NumCPU(); i++ {
@@ -133,44 +133,16 @@ func main() {
 		errors = append(errors, titleCaseErrors)
 	}
 
-	stage2Merged := mergeStringChans(ctx, stage2Channels...)
-	errorsMerged := mergeErrorChans(ctx, errors...)
+	stage2Merged := mergeChans(ctx, stage2Channels...)
+	errorsMerged := mergeChans(ctx, errors...)
 	sink(ctx, cancel, stage2Merged, errorsMerged)
 }
 
-func mergeStringChans(ctx context.Context, cs ...<-chan string) <-chan string {
+func mergeChans[T any](ctx context.Context, cs ...<-chan T) <-chan T {
 	var wg sync.WaitGroup
-	out := make(chan string)
+	out := make(chan T)
 
-	output := func(c <-chan string) {
-		defer wg.Done()
-		for n := range c {
-			select {
-			case out <- n:
-			case <-ctx.Done():
-				return
-			}
-		}
-	}
-
-	wg.Add(len(cs))
-	for _, c := range cs {
-		go output(c)
-	}
-
-	go func() {
-		wg.Wait()
-		close(out)
-	}()
-
-	return out
-}
-
-func mergeErrorChans(ctx context.Context, cs ...<-chan error) <-chan error {
-	var wg sync.WaitGroup
-	out := make(chan error)
-
-	output := func(c <-chan error) {
+	output := func(c <-chan T) {
 		defer wg.Done()
 		for n := range c {
 			select {