Destroy socket when there was an error on it (#1975)

When error happens on socket, potentially dead socket is kept open indefinitely by calling "connection.end()".
Similar issue is that it keeps socket open until long-running query is finished even though the connection was ended.

packages/pg/lib/client.js

@@ -545,7 +545,7 @@ Client.prototype.query = function (config, values, callback) {
 Client.prototype.end = function (cb) {
   this._ending = true
 
-  if (this.activeQuery) {
+  if (this.activeQuery || !this._queryable) {
     // if we have an active query we need to force a disconnect
     // on the socket - otherwise a hung query could block end forever
     this.connection.stream.destroy()

packages/pg/test/integration/connection-pool/error-tests.js

@@ -1,6 +1,7 @@
 'use strict'
 var helper = require('./test-helper')
 const pg = helper.pg
+const native = helper.args.native
 
 const suite = new helper.Suite()
 suite.test('connecting to invalid port', (cb) => {
@@ -99,3 +100,31 @@ suite.test('connection-level errors cause future queries to fail', (cb) => {
     }))
   }))
 })
+
+suite.test('handles socket error during pool.query and destroys it immediately', (cb) => {
+  const pool = new pg.Pool({ max: 1 })
+
+  if (native) {
+    pool.query('SELECT pg_sleep(10)', [], (err) => {
+      assert.equal(err.message, 'canceling statement due to user request')
+      cb()
+    })
+
+    setTimeout(() => {
+      pool._clients[0].native.cancel((err) => {
+        assert.ifError(err)
+      })
+    }, 100)
+  } else {
+    pool.query('SELECT pg_sleep(10)', [], (err) => {
+      assert.equal(err.message, 'network issue')
+      assert.equal(stream.destroyed, true)
+      cb()
+    })
+
+    const stream = pool._clients[0].connection.stream
+    setTimeout(() => {
+      stream.emit('error', new Error('network issue'))
+    }, 100)
+  }
+})