extractVarValue assumes a quote is escaped if a backslash precedes it, even if the backslash is escaped

[monerowner]

Given a .env with only one line:
FOO = "\\"

godotenv.Read(".env") will return an error because the prevChar == '\\', even though it's escaped.

// lookup quoted string terminator
for i := 1; i < len(src); i++ {
	if char := src[i]; char != quote {
		continue
	}

	// skip escaped quote symbol (\" or \', depends on quote)
	if prevChar := src[i-1]; prevChar == '\\' {
		continue
	}

	// trim quotes
	trimFunc := isCharFunc(rune(quote))
	value = string(bytes.TrimLeftFunc(bytes.TrimRightFunc(src[0:i], trimFunc), trimFunc))
	if quote == prefixDoubleQuote {
		// unescape newlines for double quote (this is compat feature)
		// and expand environment variables
		value = expandVariables(expandEscapes(value), vars)
	}

	return value, src[i+1:], nil
}

extractVarValue should instead check whether the quote symbol is preceded by an odd number of backslashes (escaped) or an even number (not escaped).