How to Convert Multiple CSV Files to Excel in Go

While CSV files are great for data storage, they aren’t always the easiest to read. If you need to share multiple CSV files with a client, converting them to Excel first is a good idea. In this brief tutorial, we will provide an API solution that will allow you to convert multiple CSV files (up to 10) to a single XLSX spreadsheet. This particular operation will provide an option to specify the worksheet names — if you don’t want to name the worksheets, they will automatically default to the CSV file names.

To call the function, simply input the target CSV files, your API key, and the worksheet names (if needed) into the following code:

package main
import (
     "fmt"
     "bytes"
     "mime/multipart"
     "os"
     "path/filepath"
     "io"
     "net/http"
     "io/ioutil"
)
func main() {
url := "https://api.cloudmersive.com/convert/csv/multi/to/xlsx"
     method := "POST"
payload := &bytes.Buffer{}
     writer := multipart.NewWriter(payload)
     file, errFile1 := os.Open("/path/to/file")
     defer file.Close()
     part1,
         errFile1 := writer.CreateFormFile("inputFile1",filepath.Base("/path/to/file"))
     _, errFile1 = io.Copy(part1, file)
     if errFile1 != nil {
          fmt.Println(errFile1)
          return
     }
     file, errFile2 := os.Open("/path/to/file")
     defer file.Close()
     part2,
         errFile2 := writer.CreateFormFile("inputFile2",filepath.Base("/path/to/file"))
     _, errFile2 = io.Copy(part2, file)
     if errFile2 != nil {
          fmt.Println(errFile2)
          return
     }
     file, errFile3 := os.Open("/path/to/file")
     defer file.Close()
     part3,
         errFile3 := writer.CreateFormFile("inputFile3",filepath.Base("/path/to/file"))
     _, errFile3 = io.Copy(part3, file)
     if errFile3 != nil {
          fmt.Println(errFile3)
          return
     }
     file, errFile4 := os.Open("/path/to/file")
     defer file.Close()
     part4,
         errFile4 := writer.CreateFormFile("inputFile4",filepath.Base("/path/to/file"))
     _, errFile4 = io.Copy(part4, file)
     if errFile4 != nil {
          fmt.Println(errFile4)
          return
     }
     file, errFile5 := os.Open("/path/to/file")
     defer file.Close()
     part5,
         errFile5 := writer.CreateFormFile("inputFile5",filepath.Base("/path/to/file"))
     _, errFile5 = io.Copy(part5, file)
     if errFile5 != nil {
          fmt.Println(errFile5)
          return
     }
     file, errFile6 := os.Open("/path/to/file")
     defer file.Close()
     part6,
         errFile6 := writer.CreateFormFile("inputFile6",filepath.Base("/path/to/file"))
     _, errFile6 = io.Copy(part6, file)
     if errFile6 != nil {
          fmt.Println(errFile6)
          return
     }
     file, errFile7 := os.Open("/path/to/file")
     defer file.Close()
     part7,
         errFile7 := writer.CreateFormFile("inputFile7",filepath.Base("/path/to/file"))
     _, errFile7 = io.Copy(part7, file)
     if errFile7 != nil {
          fmt.Println(errFile7)
          return
     }
     file, errFile8 := os.Open("/path/to/file")
     defer file.Close()
     part8,
         errFile8 := writer.CreateFormFile("inputFile8",filepath.Base("/path/to/file"))
     _, errFile8 = io.Copy(part8, file)
     if errFile8 != nil {
          fmt.Println(errFile8)
          return
     }
     file, errFile9 := os.Open("/path/to/file")
     defer file.Close()
     part9,
         errFile9 := writer.CreateFormFile("inputFile9",filepath.Base("/path/to/file"))
     _, errFile9 = io.Copy(part9, file)
     if errFile9 != nil {
          fmt.Println(errFile9)
          return
     }
     file, errFile10 := os.Open("/path/to/file")
     defer file.Close()
     part10,
         errFile10 := writer.CreateFormFile("inputFile10",filepath.Base("/path/to/file"))
     _, errFile10 = io.Copy(part10, file)
     if errFile10 != nil {
          fmt.Println(errFile10)
          return
     }
     err := writer.Close()
     if err != nil {
          fmt.Println(err)
          return
     }
client := &http.Client {
     }
     req, err := http.NewRequest(method, url, payload)
if err != nil {
          fmt.Println(err)
          return
     }
     req.Header.Add("worksheetNames", "<string>")
     req.Header.Add("Content-Type", "multipart/form-data")
     req.Header.Add("Apikey", "YOUR-API-KEY-HERE")
req.Header.Set("Content-Type", writer.FormDataContentType())
     res, err := client.Do(req)
     if err != nil {
          fmt.Println(err)
          return
     }
     defer res.Body.Close()
body, err := ioutil.ReadAll(res.Body)
     if err != nil {
          fmt.Println(err)
          return
     }
     fmt.Println(string(body))
}

Each worksheet in the resulting Excel spreadsheet will correspond to a single CSV file, enabling easy movement between the data. To retrieve your API key, visit the Cloudmersive website to register for a free account; this provides 800 monthly calls across our library of APIs.