I did many things but I do not understand a single character

pkg/API/main.go

@@ -0,0 +1,167 @@
+package main
+
+import (
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	_ "github.com/go-sql-driver/mysql"
+	"github.com/spf13/viper"
+)
+
+// Global Variables
+var db *sql.DB
+var dbUser, dbPass, dbHost, dbPort, dbName string
+
+type media struct {
+	ID        string `json: "id"`
+	YTID      string `json: "yt-id"`
+	Url       string `json: "url"`
+	Localpath string `json: "localpath"`
+	Size      int    `json: "size"`
+	Sha256sum string `json: "sha256sum"`
+	Length    int    `json: "length"`
+	Title     string `json: "title"`
+	Author    string `json: "author"`
+}
+
+// read db cred
+func readdbCred() {
+	dbCred := viper.New()
+	dbCred.SetConfigName("db-cred")
+	dbCred.AddConfigPath(".")
+	dbCred.SetConfigType("yaml")
+	err := dbCred.ReadInConfig()
+	check(err)
+	dbUser = dbCred.GetString("dbUser")
+	dbPass = dbCred.GetString("dbPass")
+	dbHost = dbCred.GetString("dbHost")
+	dbPort = dbCred.GetString("dbPort")
+	dbName = dbCred.GetString("dbName")
+	return
+}
+
+// check error
+func check(err error) {
+	if err != nil {
+		panic(err.Error())
+	}
+}
+
+func opendb() {
+	// open db
+	sqlopen := fmt.Sprintf(dbUser + ":" + dbPass + "@tcp(" + dbHost + ":" + dbPort + ")/" + dbName)
+	var err error
+	db, err = sql.Open("mysql", sqlopen)
+	check(err)
+	fmt.Println("Successfully connected to the database")
+}
+
+func dbinit(db *sql.DB) {
+	dbinit, err := db.Query("CREATE TABLE IF NOT EXISTS `media` (`id` INT NOT NULL AUTO_INCREMENT, `yt-id` VARCHAR(100), `url` VARCHAR(255), `localpath` TEXT(65535), `size` INT, `sha256sum` VARCHAR(255), `length` INT, `title` VARCHAR(255), `author` VARCHAR(255), PRIMARY KEY (`id`));")
+	if err != nil {
+		fmt.Println("Error while creating table")
+		panic(err.Error())
+	}
+	defer dbinit.Close()
+	fmt.Println("DB-Init successfull")
+}
+
+func dbentrycount(db *sql.DB) {
+	var count int
+	dbcount, err := db.Query("SELECT COUNT(*) FROM testdb.media;")
+	if err != nil {
+		fmt.Println("Error while counting rows from table")
+		panic(err.Error())
+	}
+	defer dbcount.Close()
+	for dbcount.Next() {
+		err = dbcount.Scan(&count)
+		if err != nil {
+			panic(err.Error())
+		}
+	}
+	fmt.Printf("There are %v entries in the database\n", count)
+}
+func getDB(c *gin.Context) {
+	dbquery := fmt.Sprintf("SELECT * FROM testdb.media")
+	media, err := getJSON(dbquery)
+	check(err)
+	c.IndentedJSON(http.StatusOK, media)
+}
+
+// func getMedia() []media {
+// 	dbquery := fmt.Sprintf("SELECT * FROM testdb.media")
+// 	rows, err := db.Query(dbquery)
+// 	check(err)
+// 	var MediaDB []media
+// 	for rows.Next() {
+// 		err := rows.Scan(&id, &yt-id, &url, &localpath, &size, &sha256sum, &length, &title, &author)
+// 		if err != nil {
+// 			if err == sql.ErrNoRows {
+// 				log.Println("no rows found in DB")
+// 			} else {
+// 				panic(err)
+// 			}
+// 		} else {
+// 			MediaDB = append(MediaDB, media{ID: id, YTID: yt - id, Url: url, Localpath: localpath, Size: size, Sha256sum: sha256sum, Length: length, Title: title, Author: author})
+// 		}
+// 	}
+// 	return MediaDB
+// }
+
+func getJSON(sqlString string) (string, error) {
+	rows, err := db.Query(sqlString)
+	if err != nil {
+		return "", err
+	}
+	defer rows.Close()
+	columns, err := rows.Columns()
+	if err != nil {
+		return "", err
+	}
+	count := len(columns)
+	tableData := make([]map[string]interface{}, 0)
+	values := make([]interface{}, count)
+	valuePtrs := make([]interface{}, count)
+	for rows.Next() {
+		for i := 0; i < count; i++ {
+			valuePtrs[i] = &values[i]
+		}
+		rows.Scan(valuePtrs...)
+		entry := make(map[string]interface{})
+		for i, col := range columns {
+			var v interface{}
+			val := values[i]
+			b, ok := val.([]byte)
+			if ok {
+				v = string(b)
+			} else {
+				v = val
+			}
+			entry[col] = v
+		}
+		tableData = append(tableData, entry)
+	}
+	jsonData, err := json.Marshal(tableData)
+	if err != nil {
+		return "", err
+	}
+	return string(jsonData), nil
+}
+
+func main() {
+	readdbCred()
+	opendb()
+	defer db.Close()
+
+	dbinit(db)
+	dbentrycount(db)
+
+	router := gin.Default()
+	router.GET("/api/db", getDB)
+	//router.GET("/api/songs", getMedia)
+	router.Run("127.0.0.1:8000")
+}