Add Config.Copy() in pgx and pgxpool packages. Conn.Config() and Pool.Config() return copy of the original config.

conn.go

@@ -47,6 +47,16 @@ type ConnConfig struct {
 	createdByParseConfig bool // Used to enforce created by ParseConfig rule.
 }
 
+// Copy returns a deep copy of the config that is safe to use and modify.
+// The only exception is the tls.Config:
+// according to the tls.Config docs it must not be modified after creation.
+func (cc *ConnConfig) Copy() *ConnConfig {
+	newConfig := new(ConnConfig)
+	*newConfig = *cc
+	newConfig.Config = *newConfig.Config.Copy()
+	return newConfig
+}
+
 func (cc *ConnConfig) ConnString() string { return cc.connString }
 
 // BuildStatementCacheFunc is a function that can be used to create a stmtcache.Cache implementation for connection.
@@ -425,8 +435,8 @@ func (c *Conn) StatementCache() stmtcache.Cache { return c.stmtcache }
 // ConnInfo returns the connection info used for this connection.
 func (c *Conn) ConnInfo() *pgtype.ConnInfo { return c.connInfo }
 
-// Config returns config that was used to establish this connection.
-func (c *Conn) Config() *ConnConfig { return c.config }
+// Config returns a copy of config that was used to establish this connection.
+func (c *Conn) Config() *ConnConfig { return c.config.Copy() }
 
 // Exec executes sql. sql can be either a prepared statement name or an SQL string. arguments should be referenced
 // positionally from the sql string as $1, $2, etc.