update database host configuration and add Dockerfile for containerization

Author: GabrielNat1

Dockerfile

@@ -0,0 +1,11 @@
+FROM golang:1.18
+
+WORKDIR /go/src/app
+
+COPY .  .
+
+EXPOSE 8000
+
+RUN go build -o main cmd/main.go
+
+CMD ["./main"]

db/conn.go

@@ -8,7 +8,7 @@ import (
 )
 
 const (
-	host     = "localhost"
+	host     = "go_db"
 	port     = 5432
 	user     = "postgres"
 	password = "1234"