How to Read a CSV File in Golang?

Last Updated : 26 Apr, 2023

Golang offers a vast inbuilt library that can be used to perform read and write operations on files. To read a CSV file, the following methods are used in Golang:

os.Open(): The os.Open() method opens the named file for reading. This method returns either the os.File pointer or an error.
encoding/csv: This package provides a NewReader function which is used to read a CSV file and it returns a *csv.Reader which is further used to read the contents of the file as a series of records.

Note: Use the offline compiler for better results. Save the program file with .go extension. Use the below command to execute the program:

go run filename.go

Example 1: Let us consider the CSV file named Students.csv and the contents inside the file are as follows:

S001,Thomas Hardy,CS01

S002,Christina Berglund,CS05

S003,Yang Wang,CS01

S004,Aria Cruz,CS05

S005,Hanna Moos,CS01

Below is the Golang program to read a CSV file:

// Go program to illustrate
// How to read a csv file
package main

import (
    "encoding/csv"
    "fmt"
    "log"
    "os"
)

func main() {

    // os.Open() opens specific file in
    // read-only mode and this return
    // a pointer of type os.File 
    file, err := os.Open("Students.csv")
    
    // Checks for the error
    if err != nil {
        log.Fatal("Error while reading the file", err)
    }

    // Closes the file
    defer file.Close()

    // The csv.NewReader() function is called in 
    // which the object os.File passed as its parameter 
    // and this creates a new csv.Reader that reads 
    // from the file
    reader := csv.NewReader(file)
    
    // ReadAll reads all the records from the CSV file 
    // and Returns them as slice of slices of string 
    // and an error if any
    records, err := reader.ReadAll()

    // Checks for the error
    if err != nil 
    {
        fmt.Println("Error reading records")
    }
    
    // Loop to iterate through 
    // and print each of the string slice
    for _, eachrecord := range records 
    {
        fmt.Println(eachrecord)
    }
}

Output:

Golang program to read CSV File — Fig 1.1

One can also provide a custom separator to read CSV files instead of a comma(,), by defining that in Reader struct.

Reader structure returned by NewReader function

type Reader struct{

// Comma is field delimiter set to (,) by NewReader

// which can be changed to custom delimeter

// but it must be a valid rune and it should

// not be \r,\n or unicode replacement character (0xFFFD).

Comma rune

Comment rune

FieldsPerRecord int

LazyQuotes bool

TrimLeadingSpace bool

ReuseRecord bool

TrailingComma bool

}

Example 2: Below example shows how to read a CSV file that has a custom separator. Let the CSV file be named Sample.csv and the contents in the file are as follows:

Word1-Word2

Word3-Word4

Word5-Word6