// unknown.
		{struct{ io.Reader }{strings.NewReader("xyz")}, 0},
		{io.NewSectionReader(strings.NewReader("x"), 0, 6), 0},
		{readByte(io.NewSectionReader(strings.NewReader("xy"), 0, 6)), 0},
	}
	for i, tt := range tests {
		req, err := NewRequest("POST", "http://localhost/", tt.r)
		if err != nil {
			t.Fatal(err)
		}
		if req.ContentLength != tt.want {