add initial postgres database connector

.circleci/config.yml

@@ -4,6 +4,12 @@ jobs:
   server:
     docker:
       - image: circleci/golang:1.12
+        environment:
+          - POSTGRES_CONNECTION_STRING=postgres://circle:test@localhost:5432/circle_test?sslmode=disable
+      - image: circleci/postgres:11.2-alpine
+        environment:
+          - POSTGRES_USER=circle
+          - POSTGRES_PASSWORD=test
     working_directory: ~/offen/server
     steps:
       - checkout:

docker-compose.yml

@@ -6,6 +6,14 @@ server:
     - $GOPATH/pkg/mod:/go/pkg/mod
   environment:
     - GOPATH=/go
+    - POSTGRES_CONNECTION_STRING=postgres://postgres:develop@database:5432/postgres?sslmode=disable
   ports:
     - 8080:8080
   command: go run cmd/server/main.go
+  links:
+    - database
+
+database:
+  image: postgres:11.2
+  environment:
+    - POSTGRES_PASSWORD=develop