REST API in Go example

• gorilla/mux for routing
• lib/pq PostgreSQL driver
• docker/lib/postgres as database

Source: https://semaphoreci.com/community/tutorials/building-and-testing-a-rest-api-in-go-with-gorilla-mux-and-postgresql

Project structure

• app.go - App type to provide REST web service endpoints
• handlers.go - Handle HTTP requests and execute model function calls
• main.go - main package to run service
• model.go - defines products database model and executes CRUD operations against database

CRUD of products

• create a new product: POST to /product
• delete an existing product: DELETE to /product/{id}
• update an existing product: PUT to /product/{id}
• fetch an existing product: GET to /product/{id}
• fetch a list of all existing products: GET to /products

Development Environment

Create project workspace

$ git clone https://github.com/amundsenjunior/rest-go-mux-pq.git

Get project dependencies

You can pull the two dependencies directly, via:

$ go get github.com/gorilla/mux github.com/lib/pq

Or, if using Go 1.11+, use go mod and the present go.mod and go.sum files:

$ go mod download 

Start PostgreSQL instance and create database & table

• https://hub.docker.com/_/postgres/
• https://www.postgresql.org/docs/9.2/static/app-psql.html
• https://www.tutorialspoint.com/postgresql/postgresql_create_database.htm

Either create a development database with Docker and the below SQL:

$ docker run --name rgmp -d -e POSTGRES_PASSWORD=restgomuxpq -p 5432:5432 postgres:alpine
$ docker run -it --rm --link rgmp:postgres postgres:alpine psql -h postgres -U postgres -W
  password: restgomuxpq
=# CREATE TABLE IF NOT EXISTS products (
    id SERIAL,
    name TEXT NOT NULL,
    price NUMERIC(10,2) NOT NULL DEFAULT 0.00,
    CONSTRAINT products_pkey PRIMARY KEY (id)
  );
=# \dt
=# \q

Or, build and run the database Docker image from docker/postgres, which contains an init-table.sql script of the above SQL to run on container startup:

$ docker build -t postgres:rgmp ./docker/postgres
$ docker run -d -e POSTGRES_PASSWORD=restgomuxpq -p 5432:5432 postgres:rgmp

Running the Application

Build and run the application from local source

Using the above-created Postgres Docker DB container, build the RGMP executable and run with environment variables passed in for connecting to Postgres:

$ go build
$ export DB_USERNAME=postgres DB_PASSWORD=restgomuxpq DB_NAME=postgres DB_HOST=localhost DB_PORT=5432 DB_SSLMODE=disable; ./rest-go-mux-pq

Build and run with docker-compose

Get a running application via docker-compose from the docker-compose.yaml configuration file with the following command:

$ docker-compose up -d

This instance contains both the RGMP application in a Docker container and the Postgres container, with the two services linked and initialized for taking HTTP requests. The application is up and available at http://localhost:8000.

Execute HTTP requests against the application

$ curl -X POST -H "Content-Type: application/json" -d '{"name": "toy gorilla", "price": 29.99}' http://localhost:8000/product
$ curl -X GET http://localhost:8000/products

Testing

• TestHealthStatus - expected is an OK and JSON health content
• TestEmptyTable - expected is a 200 code, but response returns 404
• TestGetNonExistentProduct - a GET request for a product by id should return error
• TestCreateProduct - an OK response code should come from a POST request of a new product
• TestGetProduct - an OK response code should come from a GET request on an existing product
• TestGetAllProducts - an OK response code and correct length of response body should come from a GET request on all existing products
• TestUpdateProduct - an OK response code should come from a PUT request on an existing product to update it
• TestDeleteProduct - an OK response code should come from a DELETE request on removing an existing product

Execute TestMain with env vars:

$ export TEST_DB_USERNAME=postgres TEST_DB_PASSWORD=restgomuxpq TEST_DB_NAME=rgmp TEST_DB_HOST=localhost TEST_DB_PORT=5432 TEST_DB_SSLMODE=disable; go test -v

Alternatively, run test_exec.sh to start a Docker test database, execute the tests, and cleanup:

$ bash ./test_exec.sh

GoDoc

• database/sql
• orilla/mux
• gorilla/handlers
• testing
• net/http
• log

References

• Original SemaphoreCI tutorial and codebase
• database/sql tutorial
• JSON encoding/decoding
• When running a db unencrypted, include 'sslmode=disable' in connection string
• Don't do local/relative imports
• When using 'go run' of multiple-file package, name all files in command