fn: add basic generic chan recv utility funcs

fn/recv.go

@@ -0,0 +1,38 @@
+package fn
+
+import (
+	"fmt"
+	"time"
+)
+
+// RecvOrTimeout attempts to recv over chan c, returning the value. If the
+// timeout passes before the recv succeeds, an error is returned
+func RecvOrTimeout[T any](c <-chan T, timeout time.Duration) (T, error) {
+	select {
+	case m := <-c:
+		return m, nil
+
+	case <-time.After(timeout):
+		var zero T
+		return zero, fmt.Errorf("timeout hit")
+	}
+}
+
+// RecvResp takes three channels: a response channel, an error channel and a
+// quit channel. If either of these channels are sent on, then the function
+// will exit with that response. This can be used to wait for a response,
+// error, or a quit signal.
+func RecvResp[T any](r <-chan T, e <-chan error, q <-chan struct{}) (T, error) {
+	var noResp T
+
+	select {
+	case resp := <-r:
+		return resp, nil
+
+	case err := <-e:
+		return noResp, err
+
+	case <-q:
+		return noResp, fmt.Errorf("quitting")
+	}
+}