diff --git a/vlib/io/buffered_reader.v b/vlib/io/buffered_reader.v
index 9ffb73548d..cf25a4f5f5 100644
--- a/vlib/io/buffered_reader.v
+++ b/vlib/io/buffered_reader.v
@@ -36,20 +36,23 @@ pub fn new_buffered_reader(o BufferedReaderConfig) &BufferedReader {
 }
 
 // read fufills the Reader interface
-pub fn (mut r BufferedReader) read(mut buf []u8) ?int {
+pub fn (mut r BufferedReader) read(mut buf []u8) !int {
 	if r.end_of_stream {
-		return none
+		return IError(Eof{})
 	}
 	// read data out of the buffer if we dont have any
 	if r.needs_fill() {
 		if !r.fill_buffer() {
 			// end of stream
-			return none
+			return IError(Eof{})
 		}
 	}
 	read := copy(mut buf, r.buf[r.offset..r.len])
 	if read == 0 {
-		return none
+		return IError(NotExpected{
+			cause: 'invalid copy of buffer'
+			code: -1
+		})
 	}
 	r.offset += read
 	return read
diff --git a/vlib/io/custom_string_reading_test.v b/vlib/io/custom_string_reading_test.v
index 87db85f1e4..f0b2f901bd 100644
--- a/vlib/io/custom_string_reading_test.v
+++ b/vlib/io/custom_string_reading_test.v
@@ -10,12 +10,12 @@ fn imin(a int, b int) int {
 	return if a < b { a } else { b }
 }
 
-fn (mut s StringReader) read(mut buf []u8) ?int {
+fn (mut s StringReader) read(mut buf []u8) !int {
 	$if debug {
 		eprintln('>>>> StringReader.read output buf.len: $buf.len')
 	}
 	if s.place > s.text.len + 1 {
-		return none
+		return IError(io.Eof{})
 	}
 	mut howmany := imin(buf.len, s.text.len - s.place)
 	xxx := s.text[s.place..s.place + howmany].bytes()
diff --git a/vlib/io/io_test.v b/vlib/io/io_test.v
index 194e61d82e..70c0c6d26e 100644
--- a/vlib/io/io_test.v
+++ b/vlib/io/io_test.v
@@ -12,9 +12,9 @@ pub mut:
 	bytes []u8
 }
 
-fn (mut b Buf) read(mut buf []u8) ?int {
+fn (mut b Buf) read(mut buf []u8) !int {
 	if !(b.i < b.bytes.len) {
-		return none
+		return IError(io.Eof{})
 	}
 	n := copy(mut buf, b.bytes[b.i..])
 	b.i += n
diff --git a/vlib/io/reader.v b/vlib/io/reader.v
index fc729b832e..6bcc77942f 100644
--- a/vlib/io/reader.v
+++ b/vlib/io/reader.v
@@ -1,13 +1,32 @@
 module io
 
+/// Eof error means that we reach the end of the stream.
+pub struct Eof {
+	Error
+}
+
+// NotExpected is a generic error that means that we receave a not expecte error.
+pub struct NotExpected {
+	cause string
+	code  int
+}
+
+fn (err NotExpected) msg() string {
+	return err.cause
+}
+
+fn (err NotExpected) code() int {
+	return err.code
+}
+
 // Reader represents a stream of data that can be read
 pub interface Reader {
 	// read reads up to buf.len bytes and places
 	// them into buf.
 	// A type that implements this should return
-	// `none` on end of stream (EOF) instead of just returning 0
+	// `io.Eof` on end of stream (EOF) instead of just returning 0
 mut:
-	read(mut buf []u8) ?int
+	read(mut buf []u8) !int
 }
 
 const (
@@ -50,7 +69,7 @@ pub fn read_any(mut r Reader) ?[]u8 {
 	mut b := []u8{len: io.read_all_len}
 	mut read := 0
 	for {
-		new_read := r.read(mut b[read..]) or { break }
+		new_read := r.read(mut b[read..]) or { return none }
 		read += new_read
 		if new_read == 0 {
 			break
diff --git a/vlib/io/reader_test.v b/vlib/io/reader_test.v
index 9cc7b35c24..3e7f72f64b 100644
--- a/vlib/io/reader_test.v
+++ b/vlib/io/reader_test.v
@@ -7,9 +7,9 @@ mut:
 	i int
 }
 
-fn (mut b Buf) read(mut buf []u8) ?int {
+fn (mut b Buf) read(mut buf []u8) !int {
 	if !(b.i < b.bytes.len) {
-		return none
+		return IError(Eof{})
 	}
 	n := copy(mut buf, b.bytes[b.i..])
 	b.i += n
@@ -44,9 +44,9 @@ mut:
 	place int
 }
 
-fn (mut s StringReader) read(mut buf []u8) ?int {
+fn (mut s StringReader) read(mut buf []u8) !int {
 	if s.place >= s.text.len {
-		return none
+		return IError(Eof{})
 	}
 	read := copy(mut buf, s.text[s.place..].bytes())
 	s.place += read
diff --git a/vlib/io/readerwriter.v b/vlib/io/readerwriter.v
index ac77500578..b03c891a09 100644
--- a/vlib/io/readerwriter.v
+++ b/vlib/io/readerwriter.v
@@ -14,7 +14,7 @@ mut:
 	w Writer
 }
 
-pub fn (mut r ReaderWriterImpl) read(mut buf []u8) ?int {
+pub fn (mut r ReaderWriterImpl) read(mut buf []u8) !int {
 	return r.r.read(mut buf)
 }
 
diff --git a/vlib/net/http/request_test.v b/vlib/net/http/request_test.v
index 1ab43d87de..98fe941f79 100644
--- a/vlib/net/http/request_test.v
+++ b/vlib/net/http/request_test.v
@@ -8,9 +8,9 @@ mut:
 	place int
 }
 
-fn (mut s StringReader) read(mut buf []u8) ?int {
+fn (mut s StringReader) read(mut buf []u8) !int {
 	if s.place >= s.text.len {
-		return none
+		return IError(io.Eof{})
 	}
 	max_bytes := 100
 	end := if s.place + max_bytes >= s.text.len { s.text.len } else { s.place + max_bytes }
diff --git a/vlib/net/openssl/ssl_connection.v b/vlib/net/openssl/ssl_connection.v
index 3de3c92ca8..78737bfd0d 100644
--- a/vlib/net/openssl/ssl_connection.v
+++ b/vlib/net/openssl/ssl_connection.v
@@ -180,8 +180,8 @@ pub fn (mut s SSLConn) socket_read_into_ptr(buf_ptr &u8, len int) ?int {
 	return res
 }
 
-pub fn (mut s SSLConn) read(mut buffer []u8) ?int {
-	res := s.socket_read_into_ptr(&u8(buffer.data), buffer.len)?
+pub fn (mut s SSLConn) read(mut buffer []u8) !int {
+	res := s.socket_read_into_ptr(&u8(buffer.data), buffer.len) or { return err }
 	return res
 }
 
diff --git a/vlib/net/tcp.v b/vlib/net/tcp.v
index 606469de18..b04c3de933 100644
--- a/vlib/net/tcp.v
+++ b/vlib/net/tcp.v
@@ -1,6 +1,7 @@
 module net
 
 import time
+import io
 import strings
 
 const (
@@ -132,8 +133,13 @@ pub fn (c TcpConn) read_ptr(buf_ptr &u8, len int) ?int {
 	return none
 }
 
-pub fn (c TcpConn) read(mut buf []u8) ?int {
-	return c.read_ptr(buf.data, buf.len)
+pub fn (c TcpConn) read(mut buf []u8) !int {
+	return c.read_ptr(buf.data, buf.len) or {
+		return IError(io.NotExpected{
+			cause: 'unexpected error in `read_ptr` function'
+			code: -1
+		})
+	}
 }
 
 pub fn (mut c TcpConn) read_deadline() ?time.Time {
diff --git a/vlib/net/websocket/io.v b/vlib/net/websocket/io.v
index 4606304a6a..b0cebd0b16 100644
--- a/vlib/net/websocket/io.v
+++ b/vlib/net/websocket/io.v
@@ -9,10 +9,10 @@ fn (mut ws Client) socket_read(mut buffer []u8) ?int {
 			return error('socket_read: trying to read a closed socket')
 		}
 		if ws.is_ssl {
-			r := ws.ssl_conn.read(mut buffer)?
+			r := ws.ssl_conn.read(mut buffer) or { return none }
 			return r
 		} else {
-			r := ws.conn.read(mut buffer)?
+			r := ws.conn.read(mut buffer) or { return none }
 			return r
 		}
 	}
diff --git a/vlib/os/file.c.v b/vlib/os/file.c.v
index db4add5c3c..7ed7897c4b 100644
--- a/vlib/os/file.c.v
+++ b/vlib/os/file.c.v
@@ -1,5 +1,24 @@
 module os
 
+/// Eof error means that we reach the end of the file.
+pub struct Eof {
+	Error
+}
+
+// NotExpected is a generic error that means that we receave a not expecte error.
+pub struct NotExpected {
+	cause string
+	code  int
+}
+
+fn (err NotExpected) msg() string {
+	return err.cause
+}
+
+fn (err NotExpected) code() int {
+	return err.code
+}
+
 pub struct File {
 mut:
 	cfile voidptr // Using void* instead of FILE*
@@ -192,11 +211,16 @@ pub fn (mut f File) reopen(path string, mode string) ? {
 }
 
 // read implements the Reader interface.
-pub fn (f &File) read(mut buf []u8) ?int {
+pub fn (f &File) read(mut buf []u8) !int {
 	if buf.len == 0 {
-		return 0
+		return IError(Eof{})
+	}
+	nbytes := fread(buf.data, 1, buf.len, f.cfile) or {
+		return IError(NotExpected{
+			cause: 'unexpected error from fread'
+			code: -1
+		})
 	}
-	nbytes := fread(buf.data, 1, buf.len, f.cfile)?
 	return nbytes
 }
 
diff --git a/vlib/os/file_test.v b/vlib/os/file_test.v
index 7acf45d88e..d1392cd6c2 100644
--- a/vlib/os/file_test.v
+++ b/vlib/os/file_test.v
@@ -130,11 +130,11 @@ fn test_read_eof_last_read_partial_buffer_fill() ? {
 	f = os.open_file(tfile, 'r')?
 	mut br := []u8{len: 100}
 	// Read first 100 bytes of 199 byte file, should fill buffer with no error.
-	n0 := f.read(mut br)?
+	n0 := f.read(mut br) or { return error('failed to read 100 bytes') }
 	assert n0 == 100
 	// Read remaining 99 bytes of 199 byte file, should fill buffer with no
 	// error, even though end-of-file was reached.
-	n1 := f.read(mut br)?
+	n1 := f.read(mut br) or { return error('failed to read 100 bytes') }
 	assert n1 == 99
 	// Read again, end-of-file was previously reached so should return none
 	// error.
@@ -143,8 +143,8 @@ fn test_read_eof_last_read_partial_buffer_fill() ? {
 		// not return a number of bytes read when end-of-file is reached.
 		assert false
 	} else {
-		// Expect none to have been returned when end-of-file.
-		assert err is none
+		// Expected an error when received end-of-file.
+		assert err !is none
 	}
 	f.close()
 }
@@ -162,11 +162,11 @@ fn test_read_eof_last_read_full_buffer_fill() ? {
 	f = os.open_file(tfile, 'r')?
 	mut br := []u8{len: 100}
 	// Read first 100 bytes of 200 byte file, should fill buffer with no error.
-	n0 := f.read(mut br)?
+	n0 := f.read(mut br) or { return error('failed to read 100 bytes') }
 	assert n0 == 100
 	// Read remaining 100 bytes of 200 byte file, should fill buffer with no
 	// error. The end-of-file isn't reached yet, but there is no more data.
-	n1 := f.read(mut br)?
+	n1 := f.read(mut br) or { return error('failed to read 100 bytes') }
 	assert n1 == 100
 	// Read again, end-of-file was previously reached so should return none
 	// error.
@@ -175,8 +175,8 @@ fn test_read_eof_last_read_full_buffer_fill() ? {
 		// not return a number of bytes read when end-of-file is reached.
 		assert false
 	} else {
-		// Expect none to have been returned when end-of-file.
-		assert err is none
+		// Expect an error at EOF.
+		assert err !is none
 	}
 	f.close()
 }
diff --git a/vlib/v/gen/js/sourcemap/vlq/vlq_decode_test.v b/vlib/v/gen/js/sourcemap/vlq/vlq_decode_test.v
index 988307e4e6..87a4479f07 100644
--- a/vlib/v/gen/js/sourcemap/vlq/vlq_decode_test.v
+++ b/vlib/v/gen/js/sourcemap/vlq/vlq_decode_test.v
@@ -35,9 +35,9 @@ fn test_decode_a() ? {
 	}
 }
 
-fn (mut b TestReader) read(mut buf []u8) ?int {
+fn (mut b TestReader) read(mut buf []u8) !int {
 	if !(b.i < b.bytes.len) {
-		return none
+		return IError(io.Eof{})
 	}
 	n := copy(mut buf, b.bytes[b.i..])
 	b.i += n