pool: implemented Role Stringer interface

implemented Role Stringer interface for human-readable printing

CHANGELOG.md

@@ -14,6 +14,7 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
   also added logs for error case of `ConnectionPool.tryConnect()` calls in 
   `ConnectionPool.controller()` and `ConnectionPool.reconnect()`
 - Methods that are implemented but not included in the pooler interface (#395).
+- Implemented stringer methods for pool.Role (#405).
 
 ### Changed
 

pool/const.go

@@ -1,3 +1,4 @@
+//go:generate stringer -type Role -linecomment
 package pool
 
 /*
@@ -31,7 +32,10 @@ const (
 type Role uint32
 
 const (
-	UnknownRole Role = iota // A connection pool failed to discover mode of the instance.
-	MasterRole              // The instance is read-write mode.
-	ReplicaRole             // The instance is in read-only mode.
+	// UnknownRole - the connection pool was unable to detect the instance mode.
+	UnknownRole Role = iota // unknown
+	// MasterRole - the instance is in read-write mode.
+	MasterRole // master
+	// ReplicaRole - the instance is in read-only mode.
+	ReplicaRole // replica
 )

pool/const_test.go

@@ -0,0 +1,13 @@
+package pool
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRole_String(t *testing.T) {
+	require.Equal(t, "unknown", UnknownRole.String())
+	require.Equal(t, "master", MasterRole.String())
+	require.Equal(t, "replica", ReplicaRole.String())
+}