How do I solve «panic: sql: unknown driver "postgres" (forgotten import?)»?

Question

I'm trying to INSERT data into POSTGRES from a .csv (pre-fixed width / tabular ) with GO.

What I've done:

package main

import (
    "bufio"
    "database/sql"
    "encoding/csv"
    "encoding/json"
    "fmt"
    "io"
    "log"
    "os"
)

type Consumidor struct {
    CPF string   `json:"CPF"`
    Private  string   `json:"Private"`
    Incompleto  string   `json:"Incompleto"`
    Compras   *Compras `json:"Compras,omitempty"`
}

type Compras struct {
    DataUltimacompra  string `json:"DataUltimacompra"`
    TicketMedio string `json:"TicketMedio"`
    TicketUltimaCompra string `json:"TicketUltimaCompra"`
    LojaMaisFrequente string `json:"LojaMaisFrequente"`
    LojaUltimaCompra string `json:"LojaUltimaCompra"`
}

const (
    host     = "localhost"
    port     = 5432
    user     = "postgres"
    password = ""
    dbname   = "neoway"
)

func main() {
    csvFile, _ := os.Open("data.csv")
    reader := csv.NewReader(bufio.NewReader(csvFile))
    var dadosinsert []Consumidor
    for {
        line, error := reader.Read()
        if error == io.EOF {
            break
        } else if error != nil {
            log.Fatal(error)
        }
        dadosinsert = append(dadosinsert, Consumidor{
            CPF: line[0],
            Private:  line[1],
            Incompleto: line[2],
            Compras: &Compras{
                DataUltimacompra:  line[3],
                TicketMedio:  line[4],
                TicketUltimaCompra: line[5],
                LojaMaisFrequente:  line[6],
                LojaUltimaCompra: line[7],

            },
        })
    }
    peopleJson, _ := json.Marshal(dadosinsert)
    fmt.Println(string(peopleJson))

    psqlInfo := fmt.Sprintf("host=%s port=%d user=%s "+
        "password=%s dbname=%s sslmode=disable",
        host, port, user, password, dbname)
    db, err := sql.Open("postgres", psqlInfo)
    if err != nil {
        panic(err)
    }
    defer db.Close()

    sqlStatement := `
INSERT INTO base_teste (CPF,"PRIVATE","INCOMPLETO","DATA DA ÚLTIMA COMPRA","TICKET MÉDIO","TICKET DA ÚLTIMA COMPRA","LOJA MAIS FREQUÊNTE","LOJA DA ÚLTIMA COMPRA")
)
VALUES ($1, $2, $3, $4, $5, $6, 7$, 8$)
RETURNING id`
    id := 0
    err = db.QueryRow(sqlStatement, 30, "a", "b", "c").Scan(&id)
    if err != nil {
        panic(err)
    }
    fmt.Println("New record ID is:", id)
}

when I run, I get this error

[{"CPF":"xxxxx","Private":"TRUE","Incompleto":"FALSE","Compras":{"DataUltimacompra":"12/10/2018","TicketMedio":"200","TicketUltimaCompra":"250","LojaMaisFrequente":"111.111.111-99","LojaUltimaCompra":"111.111.111-88"}}] panic: sql: unknown driver "postgres" (forgotten import?)

goroutine 1 [running]: main.main() C:/Users/Willian/Desktop/NEOWAY PROJECT/neoway csv prefixed width importer/main.go:70 +0xbed

Process finished with exit code 2

Answer 1

You imported the sql/database, a package contains generic interface for sql-related operation.

Since it's only generic interface, you need to import the concrete implementation of the interface, and in this context, it's the database driver.

From your code: sql.Open("postgres", psqlInfo), I presume you are using postgresql database. There are some postgresql drivers for golang available, one of them is https://github.com/lib/pq driver. So add it to the import statement.

package main

import (
    "bufio"
    "database/sql"
    "encoding/csv"
    "encoding/json"
    "fmt"
    "io"
    "log"
    "os"
    _ "github.com/lib/pq" // <------------ here
)

The database driver pq must be imported with _ character in front of the import statement. It's because we don't use it explicitly on the code meanwhile it's still required by database/sql package. For more details see this related SO question What does an underscore in front of an import statement mean?.

More information about golang sql: https://pkg.go.dev/database/sql. .