the Database field must be set on Operation - mongodb

Question

I have a golang application with mongodb connected using mongo-driver.
Everything is working fine if I run the main file as go run main.go
It is able to connect to database as expected.
However if I dockerize the application it is unable communicate to the database whenever I hit the api that interacts with the database it exits with message
the Database field must be set on Operation
Dockerfile
ARG ROOT="/go/src/bitbucket.org/myteam/myapp"
ARG BIN="/go/bin"
FROM golang:1.13 as build
ARG ROOT
ARG BIN
ENV GOBIN $BIN
ENV GOPATH /go
RUN apt-get update
RUN apt-get install go-dep -y
RUN mkdir -p $ROOT
RUN mkdir -p $BIN
WORKDIR /go
COPY .env .
WORKDIR $ROOT
COPY src/bitbucket.org/myteam/myapp .
RUN ["chmod", "+x", "main.go"]
RUN dep ensure
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo
FROM alpine:3.10
ARG ROOT
RUN apk --no-cache add ca-certificates
RUN mkdir -p /go/bin
WORKDIR /go/bin
RUN mkdir -p /go/bin
WORKDIR /go/bin
COPY --from=build $ROOT/myapp myapp
EXPOSE 3000
CMD ["./myapp"]
Connection File
config := conf.GetInstance()
ctx, _ := context.WithTimeout(context.Background(), 1*time.Second)
var clientOptions *options.ClientOptions
if config.MONGODB_USERNAME != "" && config.MONGODB_PASSWORD != "" {
if config.Env == "dev" {
clientOptions = options.Client().ApplyURI("mongodb://" + config.MONGODB_HOST + ":" + config.MONGODB_PORT).SetAuth(options.Credential{
AuthSource: config.MONGODB_NAME, Username: config.MONGODB_USERNAME, Password: config.MONGODB_PASSWORD,
})
} else {
mongoURI := fmt.Sprintf("mongodb+srv://%s:%s#%s", config.MONGODB_USERNAME, config.MONGODB_PASSWORD, config.MONGODB_HOST)
clientOptions = options.Client().ApplyURI(mongoURI)
}
} else {
clientOptions = options.Client().ApplyURI("mongodb://" + config.MONGODB_HOST + ":" + config.MONGODB_PORT)
}
client, err := mongo.Connect(ctx, clientOptions)
if err != nil {
logrus.Fatal("Error connecting to database", err)
}
db := client.Database(config.MONGODB_NAME)
Migrate(db, ctx)
logrus.Info("Database connection successful")
return db

Answer 1

This error happens when the mongodb database name is not available for the connection.
Make sure your config.MONGODB_* variables are available to set the connection string for mongodb.