Get the client working as expected with pg 8

lib/document_stores/postgres.js

@@ -1,7 +1,7 @@
 /*global require,module,process*/
 
-var postgres = require('pg');
 var winston = require('winston');
+const {Client} = require('pg');
 
 // create table entries (id serial primary key, key varchar(255) not null, value text not null, expiration int, unique(key));
 
@@ -64,13 +64,17 @@ PostgresDocumentStore.prototype = {
 
   // A connection wrapper
   safeConnect: function (callback) {
-    postgres.connect(this.connectionUrl, function (err, client, done) {
-      if (err) {
-        winston.error('error connecting to postgres', { error: err });
-        callback(err);
-      } else {
+    const client = new Client({connectionString: this.connectionUrl});
+    const connectionPromise = client.connect();
+
+    const done = () => {};
+
+    connectionPromise.then(() => {
       callback(undefined, client, done);
-      }
+    }).catch((error) => {
+      console.log(error);
+      winston.error('error connecting to postgres', {error});
+      callback(error);
     });
   }