From fe366b2cf31b42e6736925f61b187cd0c38b1d2e Mon Sep 17 00:00:00 2001
From: Matt Schultz <matt@hmbradley.com>
Date: Tue, 16 Mar 2021 18:07:24 -0500
Subject: [PATCH] Prevent panics caused by attempting to close an already
 closed pgxpool.Pool.

---
 pgxpool/pool.go      | 10 ++++++++--
 pgxpool/pool_test.go | 11 +++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/pgxpool/pool.go b/pgxpool/pool.go
index 09752aaa..650c5970 100644
--- a/pgxpool/pool.go
+++ b/pgxpool/pool.go
@@ -326,8 +326,14 @@ func ParseConfig(connString string) (*Config, error) {
 // Close closes all connections in the pool and rejects future Acquire calls. Blocks until all connections are returned
 // to pool and closed.
 func (p *Pool) Close() {
-	close(p.closeChan)
-	p.p.Close()
+	// Check to see if the closeChan is closed before attempting to close it again, which can result in a panic.
+	select {
+	case <-p.closeChan:
+		// NOOP because the channel is already closed.
+	default:
+		close(p.closeChan)
+		p.p.Close()
+	}
 }
 
 func (p *Pool) backgroundHealthCheck() {
diff --git a/pgxpool/pool_test.go b/pgxpool/pool_test.go
index 965f342f..f6621df6 100644
--- a/pgxpool/pool_test.go
+++ b/pgxpool/pool_test.go
@@ -789,3 +789,14 @@ func TestTxBeginFuncNestedTransactionRollback(t *testing.T) {
 	require.NoError(t, err)
 	require.EqualValues(t, 2, n)
 }
+
+func TestIdempotentPoolClose(t *testing.T) {
+	pool, err := pgxpool.Connect(context.Background(), os.Getenv("PGX_TEST_DATABASE"))
+	require.NoError(t, err)
+
+	// Close the open pool.
+	require.NotPanics(t, func() { pool.Close() })
+
+	// Close the already closed pool.
+	require.NotPanics(t, func() { pool.Close() })
+}