How to Handle Dynamic Database Connections in Go? - postgresql

Question

I am currently building a Go application that needs to connect to multiple databases dynamically.
For context I have 22 Databases (db1, db2, db3...) and the dbUser, dbPass and dbPort remains the same. To determine which database to connect to, I need access to the query param in echo before database connection.
I need a solution to connect to the right database efficiently. What are some best practices and methods for achieving this in Go?
Main.go
package main
import (
"database/sql"
"fmt"
"log"
"time"
_ "github.com/go-sql-driver/mysql"
_ "github.com/lib/pq"
"github.com/labstack/echo"
"github.com/spf13/viper"
_variantHttpDelivery "backend/server/variant/delivery/http"
_variantHttpDeliveryMiddleware "backend/server/variant/delivery/http/middleware"
_variantRepo "backend/server/variant/repository/postgres"
_variantUcase "backend/server/variant/usecase"
)
func init() {
viper.SetConfigFile(`config.json`)
err := viper.ReadInConfig()
if err != nil {
panic(err)
}
if viper.GetBool(`debug`) {
log.Println("Service RUN on DEBUG mode")
}
}
func main() {
dbHost := viper.GetString(`database.host`)
dbPort := viper.GetString(`database.port`)
dbUser := viper.GetString(`database.user`)
dbPass := viper.GetString(`database.pass`)
dbName := viper.GetString(`database.name`)
connection := fmt.Sprintf("postgresql://%s:%s#%s:%s/%s", dbUser, dbPass, dbHost, dbPort, dbName)
dsn := fmt.Sprintf("%s?%s", connection)
dbConn, err := sql.Open(`postgres`, dsn)
log.Println("Connection Successful 👍")
if err != nil {
log.Fatal(err)
}
err = dbConn.Ping()
if err != nil {
log.Fatal(err)
}
defer func() {
err := dbConn.Close()
if err != nil {
log.Fatal(err)
}
}()
e := echo.New()
middL := _variantHttpDeliveryMiddleware.InitMiddleware()
e.Use(middL.CORS)
variantRepo := _variantRepo.NewPsqlVariantRepository(dbConn)
timeoutContext := time.Duration(viper.GetInt("context.timeout")) * time.Second
au := _variantUcase.NewVariantUsecase(variantRepo, timeoutContext)
_variantHttpDelivery.NewVariantHandler(e, au)
log.Fatal(e.Start(viper.GetString("server.address"))) //nolint
}
Repository which handles all the database logic
package postgres
import (
"backend/server/domain"
"context"
"database/sql"
"github.com/sirupsen/logrus"
"reflect"
)
type psqlVariantRepository struct {
Conn *sql.DB
}
// NewPsqlVariantRepository will create an object that represent the variant.Repository interface
func NewPsqlVariantRepository(conn *sql.DB) domain.VariantRepository {
return &psqlVariantRepository{conn}
}
func (m *psqlVariantRepository) GetByVCF(ctx context.Context, vcf string) (res domain.Variant, err error) {
query := `SELECT * FROM main1 WHERE variant_vcf = $1`
list, err := m.fetch(ctx, query, vcf)
if err != nil {
return domain.Variant{}, err
}
if len(list) > 0 {
res = list[0]
} else {
return res, domain.ErrNotFound
}
return
}
func (m *psqlVariantRepository) fetch(ctx context.Context, query string, args ...interface{}) (result []domain.Variant, err error) {
rows, err := m.Conn.QueryContext(ctx, query, args...)
if err != nil {
logrus.Error(err)
return nil, err
}
defer func() {
errRow := rows.Close()
if errRow != nil {
logrus.Error(errRow)
}
}()
result = make([]domain.Variant, 0)
for rows.Next() {
t := domain.Variant{}
values := make([]interface{}, 0, reflect.TypeOf(t).NumField())
v := reflect.ValueOf(&t).Elem()
for i := 0; i < v.NumField(); i++ {
if v.Type().Field(i).Type.Kind() == reflect.String {
values = append(values, new(sql.NullString))
} else {
values = append(values, v.Field(i).Addr().Interface())
}
}
err = rows.Scan(values...)
if err != nil {
logrus.Error(err)
return nil, err
}
for i, value := range values {
if ns, ok := value.(*sql.NullString); ok {
v.Field(i).SetString(ns.String)
}
}
result = append(result, t)
}
logrus.Info("Successfully fetched results from database 👍")
return result, nil
}
So far I couldn't find any solution