})
		} else {
			vv := header[key]
			if vv == nil && len(strs) > 0 {
				// More than likely this will be a single-element key.
				// Most headers aren't multi-valued.
				// Set the capacity on strs[0] to 1, so any future append
				// won't extend the slice into the other strings.
				vv, strs = strs[:1:1], strs[1:]
				vv[0] = hf.Value
				header[key] = vv
			} else {