Always quote csv values

I want to quote all fields in a CSV document. Is there a way to modify golang's csv module without having to copy all the code? In another language, I'd simply inherit from csv.Writer and override fieldNeedsQuotes, but that is not possible in Go, or is it?

I see, it's an old question. But I recently faced the same problem, and created a small library altcsv, by extending the Golang's encoding/csv.

If someone else is wondering about the same, you can use the below library:
https://github.com/tushar2708/altcsv

It's backward compatible with existing CSV library. I plan to add more python-like CSV interface to the same in future.

Reading from a CSV file:

fileRdr, _ = os.Open("/tmp/custom_csv_file.txt")
csvRdr := altcsv.NewReader(fileRdr)
content := csvReader.ReadAll()

Writing to a CSV file:

headers = []string{"hero_name", "alter_ego", "identity"}
fileWtr, _ := os.Create("/tmp/all_quotes_csv_file.txt")
csvWtr := altcsv.NewWriter(csvH)
csvWtr.AllQuotes = true   // surround each field with '"'
csvWtr.Write(headers)
csvWtr.Write([]string{"Spider-Man", "Peter Parker", "Secret Identity"})
csvWtr.Write([]string{"Captain America", "Steven Rogers", "Public Identity"})
csvWtr.Write([]string{"Thor", "Thor Odinson", "No dual Identity"})
csvWtr.Flush()
fileWtr.Close()

Matt and Volker already said that you can copy the module and modify it.

You can use a Writer wrapper as well, but I think it's a bit more complex.
See my attempt as a proof of concept (not to be used*).

type quoteWriter struct {
	w io.Writer
}

func (w quoteWriter) Write(p []byte) (n int, err error) {
	q := make([]byte, 0)
	quoted := true
	quoted = (p[0] == '"')
	if !quoted {
		//begin field quote
		q = append(q, '"')
	}

	for i, v := range p {
		//We check the "quotation" status for new field or line
		//This is a simplification
		if v == ',' || v == '\n' {
			if !quoted { //end field quote
				q = append(q, '"')
			}
			//copy current byte
			q = append(q, v)

			//is next byte quote?
			if len(p) > i+1 {
				quoted = (p[i+1] == '"')
			}
			if !quoted { //begin field quote
				q = append(q, '"')
			}
		} else {
			q = append(q, v)
		}
	}

	return w.w.Write(q)
}

See below the example coming from the csv#Writer test (http://golang.org/src/pkg/encoding/csv/writer_test.go) with the proof of concept applied:

http://play.golang.org/p/wovYUkt6Vq

not to be used* Please, notice that I haven't checked all cases, for instance, if a comma is within a quoted text or not, so you would need to check and adapt it.
I also recommend to copy and modify the csv package.