How to Convert Multiple CSV Files into a Single XLSX Spreadsheet using Go

Converting between common data formats is a rudimentary & essential task for individuals and businesses everywhere. Given the interoperability of XLSX format, it’s no surprise that CSV to XLSX conversions fit right into that meta.

In this article, I’ll demonstrate a Cloudmersive API (using ready-to-run, copy & paste Go code examples provided below) which will allow you take control of this common conversion need. This API specifically converts multiple CSV files into a single XLSX spreadsheet — with one worksheet corresponding to each CSV File — and it allows up to 10 CSV file inputs at a time, with the option to specify the name of each worksheet (as a string) within the API parameters. To use this API for free, just register a free account on our website and use your free-tier API key to authenticate your API call.

To call the API function, all you need to do is copy the below code into your environment and include your API key in the correct field as a string. After configuring your file inputs, you can then generate the encoding for your new multi-worksheet file:

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))
}

All done!