How to Build an API with Echo Golang and GraphQL using gqlgen (Part I)
This article is made to serve as a reference for building APIs using Golang’s Echo framework and gqlen as GraphQL library trying to use the best architecture and software development practices.
Prerequisites
- Golang Installed (https://golang.org/doc/install)
Step 1: Build your API template
- For the development of the APIwe will take as a basis this project that contains the basic implementation of a REST API with the use of a layered architecture, injection of dependencies, unit tests,go mods
Step 2: Initialise your Go project as gqlgen project
For the next step we need to go to the directory in which our API is located and run the next commands to initialize it as a gqlgen project which will generate the serve code
go get github.com/99designs/gqlgen
go run github.com/99designs/gqlgen init --verbose
You will see that the files containing the graphQL functionality have been added to the project
As you can see, gqlgen generates an implementation of a server to be able to run the API at server.go. This causes conflicts within the api because we have a main method already implemented, up to this point it would not be possible to run our API due to these conflicts
Then our next step would be to couple the gqlgen-generated auto server implementation with the one we have with Echo, let’s start by preserving a single line of code from the server.go file and then deleting it
srv:=handler.NewDefaultServer(generated.NewExecutableSchema(generated.Config{Resolvers: &graph.Resolver{}}))now we will modify the container.go file, adding a method that injects the graphql schema to the server as below :
Step 3 Start Our Implementation :D
Now we generate the server code for our schema, for practical purposes we will reuse the schema that gqlgen autogenerated, which is found in /graph/schema.graphqlwhich already contains the definition of querys and mutations. Now run the gqlgen generate command to generate Go models, resolvers and a dummy server implementation for our schema.
go run github.com/99designs/gqlgen generate --verboseGqlgen allows us to control and customize the code that is going to be generated. From changing the location of the schema, bind our existing models with those defined in the schema to avoid their auto-generation, enable Apollo Federation and a host of other things.
Now the next step.Following the principles of layered architecture, we will continue with the creation of some more files; this to begin to segregate responsibilities.We will add our repository layer in which the database request, APIs Rest, GRPC or any other data source, will be added. In this case it will be a mock. We will also add our service layer which will be in charge of orchestrating the business logic and will be responsible for calling and managing our data layer. So we add an services folder to include ITodoService.go ,todoService.go files , and ITodoRepository.go todoRepository.go at repositories folder.
Now we are going to edit the file reolver.goto add the DI
And then we go to our schema.resolvers.gofile to modify it and add our implementation of the resolver
we add our new methods for DI to the file container.go and we are going to eliminate the method to use the DI of the resolver
Now as the last step we are going to register the graphQL route in our server generating the executable schema from the resolver generated by the DI
It is necessary to wrap the handlerQL as an echo Handler func, so that it recognizes it as a valid handler function
Step 4 Let´s Try !!
So now we can run our API by executing the command go run main.go
Let´s do a request using GraphiQL client and we can see the schema at the Docs explorer
Next Steps
How to get echo context to use with gqlgen, integration of Grpc as data source …. etc etc :D
