A function to convert an array into csv file in go.

csv.go

package util

import (
	"encoding/csv"
	"fmt"
	"io"
	"reflect"
)

// StreamCsv converts an array of an struct to csv
// The headers of struct is found using reflection and json tag in the struct
// Will panic if data is not slice
// Behaviour is undefined if elements of slice have different types
func StreamCsv(w io.Writer, data interface{}) error {
	// At first ensure that the data is a slice
	if reflect.TypeOf(data).Kind() != reflect.Slice {
		panic("data is not an slice")
	}
	// If the length is zero, do nothing
	dataValue := reflect.ValueOf(data)
	if dataValue.Len() == 0 {
		return nil
	}
	// Start the writer...
	writer := csv.NewWriter(w)
	defer writer.Flush()
	var err error
	// At first get the headers
	var indexes []int
	{
		first := dataValue.Index(0).Type()
		headersCount := first.NumField()
		header := make([]string, 0, headersCount)
		indexes = make([]int, 0, headersCount)
		for i := 0; i < headersCount; i++ {
			if tag, exists := first.Field(i).Tag.Lookup("csv"); exists {
				header = append(header, tag)
				indexes = append(indexes, i)
			}
		}
		err = writer.Write(header)
		if err != nil {
			return err
		}
	}
	// Now write all data in the array
  row := make([]string, len(indexes))
	for i := 0; i < dataValue.Len(); i++ {
		now := dataValue.Index(i)
		for j, index := range indexes {
			row[j] = fmt.Sprintf("%v", now.Field(index))
		}
		err = writer.Write(row)
		if err != nil {
			return err
		}
	}
	return nil
}