Don't remove connection from the pool on redis errors.

error.go

@@ -0,0 +1,23 @@
+package redis
+
+import (
+	"fmt"
+)
+
+// Redis nil reply.
+var Nil = errorf("redis: nil")
+
+// Redis transaction failed.
+var TxFailedErr = errorf("redis: transaction failed")
+
+type redisError struct {
+	s string
+}
+
+func errorf(s string, args ...interface{}) redisError {
+	return redisError{s: fmt.Sprintf(s, args...)}
+}
+
+func (err redisError) Error() string {
+	return err.s
+}