https://dev.to/hekonsek/go-interview-task-example-rest-api-54ld

Dockerfile

FROM golang:1.16 as compile

WORKDIR /weather
COPY . /weather
RUN CGO_ENABLED=0 GOOS=linux GOPROXY=https://proxy.golang.org go build -o weather main.go

FROM alpine:latest
EXPOSE 8080
RUN apk --no-cache add ca-certificates && addgroup -S weather && adduser -S weather -G weather
USER weather
WORKDIR /weather
COPY --from=compile /weather/weather .
ENTRYPOINT ["./weather"]

main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
)

const (
	port         = ":8080"
	defaultState = "NY"
)

// APIResponse struct uses only the fields we need to fullfil the objective
type APIResponse struct {
	Features []struct {
		Properties struct {
			Headline string `json:"headline"`
		} `json:"properties"`
	} `json:"features"`
}

// AlertsResponse struct format for our output
type AlertsResponse struct {
	Alerts []string `json:"alerts"`
}

// getAlerts retrieves weather alerts by state and returns []byte's of JSON
func getAlerts(state string) ([]byte, error) {
	if state == "" {
		state = defaultState
	}
	url := fmt.Sprintf("https://api.weather.gov/alerts/active?area=%s", state)
	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return nil, err
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, err
	}

	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	var alert APIResponse
	err = json.Unmarshal(body, &alert)
	if err != nil {
		return nil, err
	}

	var alerts AlertsResponse
	for c := range alert.Features {
		alerts.Alerts = append(alerts.Alerts, alert.Features[c].Properties.Headline)
	}
	jsn, err := json.Marshal(alerts)
	if err != nil {
		return nil, err
	}

	if err != nil {
		return nil, err
	}
	return jsn, nil
}

func main() {
	http.HandleFunc("/ping", func(w http.ResponseWriter, r *http.Request) {
		fmt.Fprintf(w, "pong")
	})

	http.HandleFunc("/api/weather", func(w http.ResponseWriter, r *http.Request) {
		// Could get state from a URL param but that's not the spec.
		jsn, err := getAlerts("")
		if err != nil {
			log.Println(err)
			http.Error(w, http.StatusText(http.StatusInternalServerError),
				http.StatusInternalServerError)
		} else {
			fmt.Fprintf(w, string(jsn))
		}
	})

	err := http.ListenAndServe(port, nil)
	if err != nil {
		log.Fatal(err)
	}
}