Replace all spaces in a string with '+'

Documentation on strings.Replace(): http://golang.org/pkg/strings/#Replace

According to the documentation, the fourth integer parameter is the number of replacements. Your example would only replace the first space with a "+". You need to use a number less than 0 for it to not impose a limit:

tw.Text = strings.Replace(tw.Text, " ", "+", -1)

Use strings.ReplaceAll

tw.Text = strings.ReplaceAll(tw.Text, " ", "+")

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If you're using an older version of go (< 1.12), use strings.Replace with -1 as limit (infinite)

tw.Text = strings.Replace(tw.Text, " ", "+", -1)