io: fix detection of end_of_stream, when reading files through io.new_buffered_reader(reader: io.make_reader(f))

vlib/io/os_file_reader_test.v

@@ -0,0 +1,29 @@
+import os
+import io
+
+fn read_file(file string, cap int) []string {
+	mut lines := []string{}
+	mut f := os.open(file) or { panic(err) }
+	defer {
+		f.close()
+	}
+	mut r := io.new_buffered_reader(reader: io.make_reader(f), cap: cap)
+	for {
+		l := r.read_line() or { break }
+		lines << l
+		// println('Line: $l')
+	}
+	assert lines.len > 0
+	assert r.end_of_stream == true
+	println('------------------------------------------------ cap: ${cap:6}; read: ${lines.len:3} lines')
+	return lines
+}
+
+fn test_file_reader() {
+	for cap := 64; cap <= 10000; cap += 256 {
+		lines := read_file(@FILE, cap)
+		assert lines.last() == '// my last line'
+	}
+}
+
+// my last line