Implement user API

+
+# Created by https://www.toptal.com/developers/gitignore/api/go,vscode
+# Edit at https://www.toptal.com/developers/gitignore?templates=go,vscode
+
+### Go ###
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/
+
+### Go Patch ###
+/vendor/
+/Godeps/
+
+### vscode ###
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+*.code-workspace
+
+# End of https://www.toptal.com/developers/gitignore/api/go,vscode
+
+__debug_bin
+config.json
\ No newline at end of file

+package main
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/gorilla/mux"
+
+	_ "github.com/go-sql-driver/mysql"
+	"github.com/jmoiron/sqlx"
+)
+
+type App struct {
+	Config Config
+	db     *sqlx.DB
+	router *mux.Router
+}
+
+func NewApp(config Config) *App {
+	app := new(App)
+	app.Config = config
+
+	dsn := fmt.Sprintf("%s:%s@tcp(%s)/%s", config.Database.User, config.Database.Password, config.Database.Host, config.Database.Name)
+	app.db = sqlx.MustOpen("mysql", dsn)
+
+	app.router = mux.NewRouter()
+	app.router.HandleFunc("/users", app.PostUsers).Methods("POST")
+	app.router.HandleFunc("/users/tokens", app.PostTokens).Methods("POST")
+
+	return app
+}
+
+func (app *App) Serve() {
+	http.ListenAndServe(fmt.Sprintf(":%d", app.Config.Port), app.router)
+}

+package main
+
+import (
+	"encoding/json"
+	"io/ioutil"
+)
+
+type Config struct {
+	Port     int `json:"port"`
+	Database struct {
+		Host     string `json:"host"`
+		Name     string `json:"name"`
+		User     string `json:"user"`
+		Password string `json:"password"`
+	} `json:"database"`
+	TokenSecret string `json:"token_secret"`
+}
+
+func LoadConfig(path string) (Config, error) {
+	config := Config{}
+
+	data, err := ioutil.ReadFile(path)
+	if err == nil {
+		err = json.Unmarshal(data, &config)
+	}
+
+	return config, err
+}

+module mf-server
+
+go 1.15
+
+require (
+	github.com/dgrijalva/jwt-go v3.2.0+incompatible
+	github.com/go-sql-driver/mysql v1.5.0
+	github.com/gorilla/mux v1.8.0
+	github.com/jmoiron/sqlx v1.2.0
+	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897
+)

+github.com/dgrijalva/jwt-go v1.0.2 h1:KPldsxuKGsS2FPWsNeg9ZO18aCrGKujPoWXn2yo+KQM=
+github.com/dgrijalva/jwt-go v3.2.0+incompatible h1:7qlOGliEKZXTDg6OTjfoBKDXWrumCAMpl/TFQ4/5kLM=
+github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
+github.com/go-sql-driver/mysql v1.4.0/go.mod h1:zAC/RDZ24gD3HViQzih4MyKcchzm+sOG5ZlKdlhCg5w=
+github.com/go-sql-driver/mysql v1.5.0 h1:ozyZYNQW3x3HtqT1jira07DN2PArx2v7/mN66gGcHOs=
+github.com/go-sql-driver/mysql v1.5.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
+github.com/gorilla/mux v1.8.0 h1:i40aqfkR1h2SlN9hojwV5ZA91wcXFOvkdNIeFDP5koI=
+github.com/gorilla/mux v1.8.0/go.mod h1:DVbg23sWSpFRCP0SfiEN6jmj59UnW/n46BH5rLB71So=
+github.com/jmoiron/sqlx v1.2.0 h1:41Ip0zITnmWNR/vHV+S4m+VoUivnWY5E4OJfLZjCJMA=
+github.com/jmoiron/sqlx v1.2.0/go.mod h1:1FEQNm3xlJgrMD+FBdI9+xvCksHtbpVBBw5dYhBSsks=
+github.com/lib/pq v1.0.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
+github.com/mattn/go-sqlite3 v1.9.0/go.mod h1:FPy6KqzDD04eiIsT53CuJW3U88zkxoIYsOqkbpncsNc=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 h1:pLI5jrR7OSLijeIDcmRxNmw2api+jEfxLoykJVice/E=
+golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

+package main
+
+import (
+	"log"
+)
+
+func main() {
+	config, err := LoadConfig("config.json")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	app := NewApp(config)
+	app.Serve()
+}

+package main
+
+import (
+	"encoding/json"
+	"net/http"
+	"time"
+
+	"github.com/dgrijalva/jwt-go"
+	"github.com/go-sql-driver/mysql"
+	"golang.org/x/crypto/sha3"
+)
+
+type User struct {
+	No        uint64    `json:"no"`
+	ID        string    `json:"id"`
+	Name      string    `json:"name"`
+	CreatedAt time.Time `json:"created_at"`
+	ExpiredAt time.Time `json:"expired_at"`
+}
+
+func (app *App) PostUsers(w http.ResponseWriter, r *http.Request) {
+	body := make(map[string]interface{})
+	err := json.NewDecoder(r.Body).Decode(&body)
+	if err != nil {
+		WriteJson(w, http.StatusBadRequest, map[string]interface{}{"msg": "Failed to parse request json"})
+		return
+	}
+
+	hash := sha3.Sum256([]byte(body["password"].(string)))
+
+	res, err := app.db.Exec("INSERT INTO users (`id`, `password`, `name`) VALUES (?, ?, ?)", body["id"], hash[:], body["name"])
+	if err != nil {
+		if merr, ok := err.(*mysql.MySQLError); ok {
+			if merr.Number == 1062 {
+				WriteJson(w, http.StatusConflict, map[string]interface{}{"msg": "Already registered"})
+				return
+			}
+		}
+
+		WriteJson(w, http.StatusInternalServerError, map[string]interface{}{"msg": "Failed to register"})
+		return
+	}
+
+	no, _ := res.LastInsertId()
+	WriteJson(w, http.StatusOK, map[string]interface{}{"user_no": no})
+}
+
+func (app *App) PostTokens(w http.ResponseWriter, r *http.Request) {
+	body := make(map[string]interface{})
+	err := json.NewDecoder(r.Body).Decode(&body)
+	if err != nil {
+		WriteJson(w, http.StatusBadRequest, map[string]interface{}{"msg": "Failed to parse request json"})
+		return
+	}
+
+	hash := sha3.Sum256([]byte(body["password"].(string)))
+	rows, err := app.db.Query("SELECT `no` FROM users WHERE `id`=? AND `password`=?", body["id"], hash[:])
+	if err != nil {
+		WriteJson(w, http.StatusInternalServerError, map[string]interface{}{"msg": "Failed to register"})
+		return
+	}
+
+	if !rows.Next() {
+		WriteJson(w, http.StatusUnauthorized, map[string]interface{}{"msg": "Login failed"})
+		return
+	}
+
+	no := uint64(0)
+	rows.Scan(&no)
+
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{"no": no})
+	auth, err := token.SignedString([]byte(app.Config.TokenSecret))
+	if err != nil {
+		WriteJson(w, http.StatusInternalServerError, map[string]interface{}{"msg": "Login failed"})
+		return
+	}
+
+	WriteJson(w, http.StatusOK, map[string]interface{}{"token": auth})
+}

+package main
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+func WriteJson(w http.ResponseWriter, status int, data interface{}) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	json.NewEncoder(w).Encode(data)
+}