Failure to load TOML data with spaces in a dotted key assignment

[x-hgg-x]

Describe the bug
Loading produces an error:

(1, 5): was expecting token =, but got "." instead

To Reproduce

_, err := toml.Load(` S1 . 'S2' . "S3" = 3`)
if err != nil {
	fmt.Println(err)
}

Expected behavior
There should be no error according to the TOML specification:

Whitespace around dot-separated parts is ignored.

Versions

• go-toml: last version of master (9ccd9bb)
• go: 1.14
• operating system: Linux

Additional context
The following code works:

_, err := toml.Load(`[ S1 . 'S2' . "S3" ]`)
if err != nil {
	fmt.Println(err)
}