diff --git a/bar.cr b/bar.cr
new file mode 100644
index 000000000000..ef9edd1a1144
--- /dev/null
+++ b/bar.cr
@@ -0,0 +1,31 @@
+require "logger"
+
+module Migrate::Logging
+  @@logger : Logger  = Logger.new(STDOUT).tap do |l|
+     l.formatter = Logger::Formatter.new do |severity, datetime, progname, message, io|
+ 	    io << severity[0] << ", [" << datetime << " #" << Process.pid << "] "
+     	io << severity.rjust(5) << " -- " << progname << ": " << message
+   	  io << "My additional suff"
+ 	  end
+  end
+
+  def logger
+    @@logger
+  end
+
+  def self.logger
+    @@logger
+  end
+end
+
+class Foo
+  include Migrate::Logging
+  def foo
+    logger.warn("Hello!")
+    42
+  end
+end
+
+Foo.new.foo
+
+    
diff --git a/foo b/foo
new file mode 100755
index 000000000000..eaf3d7ce0470
Binary files /dev/null and b/foo differ
diff --git a/foo.cr b/foo.cr
new file mode 100644
index 000000000000..7785637b6171
--- /dev/null
+++ b/foo.cr
@@ -0,0 +1,5 @@
+# puts "A"
+# spawn do
+#   puts "B"
+# end
+# puts "C"
diff --git a/io_deferred b/io_deferred
new file mode 100755
index 000000000000..a119b1baff5b
Binary files /dev/null and b/io_deferred differ
diff --git a/io_deferred.cr b/io_deferred.cr
new file mode 100644
index 000000000000..9c7b564d2318
--- /dev/null
+++ b/io_deferred.cr
@@ -0,0 +1,175 @@
+module IO
+  def self.deferred(&block : IO -> Void)
+    IO::Deferred.new(block).reader
+  end
+end
+
+class IO::Deferred
+  include IO
+
+  @target : Bytes?
+  @raw : Bytes
+  @buffer : Bytes
+
+  @chan_reader : Channel(Int32)
+  @chan_writer : Channel(Int32)
+  @chan_block : Channel(Nil)
+
+  @started : Bool
+  @finished : Bool
+
+  @reader : Reader?
+  @writer : Writer?
+
+  def initialize(@block : IO -> Void)
+    @raw = Bytes.new(4096)
+    @buffer = Bytes.new(@raw.to_unsafe, 0)
+    @chan_reader = Channel(Int32).new
+    @chan_writer = Channel(Int32).new
+    @chan_block = Channel(Nil).new
+    @started = false
+    @finished = false
+  end
+
+  def read(target : Bytes)
+    puts "READING 1"
+
+    try_start
+    written = 0
+
+    puts "READING 2"
+
+    # Store the requested target buffer to be written in the `write` method
+    @target = target
+
+    # Grab what's leftover in the buffer, if any
+    if @buffer.size > 0
+      writeable_size = [@buffer.size, target.size].min
+      target.copy_from(@buffer.to_unsafe, writeable_size)
+      @buffer += writeable_size
+      target += writeable_size
+      written += writeable_size
+    end
+
+    # Unblock the writing fiber only if the buffer did not cover the read request,
+    # and block until the write method signals us that the write was completed
+    while target.size > 0 && !@finished
+      @chan_writer.send(target.size)
+      select
+      when bytes = @chan_reader.receive
+        written += bytes
+      when @chan_block.receive
+        @finished = true
+      end
+    end
+
+    @target = nil
+    return written
+  end
+
+  def write(source : Bytes)
+    # Block until the main reader fiber signals us for a write request
+    requested = @chan_writer.receive
+
+    # Write to the target slice
+    target = @target.not_nil!
+    writeable_size = [target.size, source.size].min
+    target.copy_from(source.to_unsafe, writeable_size)
+    source += writeable_size
+
+    # Store leftover (if any) in buffer, resizing underlying raw buffer if needed
+    if source.size > 0
+      @raw = Bytes.new(source.size) if source.size > @raw.size
+      @raw.copy_from(source.to_unsafe, source.size)
+    end
+
+    # Update buffer view of raw underlying buffer
+    @buffer = Bytes.new(@raw.to_unsafe, source.size)
+
+    # Signal the reader fiber that this write operation is finished,
+    # sending the number of bytes written to target
+    @chan_reader.send(writeable_size)
+
+    return nil
+  end
+
+  def reader
+    @reader ||= Reader.new(self)
+    puts "Yielding reader"
+    @reader.not_nil!
+  end
+
+  def writer
+    @writer ||= Writer.new(self)
+    puts "Yielding writer"
+    @writer.not_nil!
+  end
+
+  def try_start
+    unless @started
+      @started = true
+      spawn do
+        @block.call(writer)
+        @chan_block.send(nil)
+      end
+    end
+  end
+end
+
+class IO::Deferred::Reader
+  include IO
+
+  def initialize(@io : IO::Deferred)
+  end
+
+  def read(slice : Bytes)
+    @io.read(slice)
+  end
+
+  def write(slice : Bytes)
+    raise IO::Error.new("can't write to IO::Deferred::Reader")
+  end
+end
+
+class IO::Deferred::Writer
+  include IO
+
+  def initialize(@io : IO::Deferred)
+  end
+
+  def read(slice : Bytes)
+    raise IO::Error.new("can't read from IO::Deferred::Writer")
+  end
+
+  def write(slice : Bytes)
+    @io.write(slice)
+  end
+end
+
+puts "Before Starting"
+
+reader = IO.deferred do |writer|
+  puts "BLOCK | Initialising writer"
+  4.times do
+    puts "BLOCK | Writing 6 bytes"
+    writer.write("foobar".to_slice)
+  end
+end
+
+puts "Starting"
+# puts reader.read_string(6)
+# puts "1"
+# puts reader.read_string(6)
+# puts "2"
+# puts reader.read_string(6)
+# puts "3"
+# puts reader.read_string(6)
+# puts "4"
+# puts reader.read_string(6)
+# puts "5"
+# puts reader.read_string(6)
+# puts "6"
+# # puts reader.read_string(1)
+# # puts reader.read_string(1)
+# # puts reader.read_string(16)
+# # puts reader.gets_to_end
diff --git a/spec/std/openssl/digest_io_spec.cr b/spec/std/openssl/digest_io_spec.cr
index 6b3fb3a450d8..e57035a96365 100644
--- a/spec/std/openssl/digest_io_spec.cr
+++ b/spec/std/openssl/digest_io_spec.cr
@@ -31,7 +31,7 @@ describe OpenSSL::DigestIO do
     base_io = IO::Memory.new("foo")
     base_digest = OpenSSL::Digest.new("SHA256")
     empty_digest = OpenSSL::Digest.new("SHA256").digest
-    io = OpenSSL::DigestIO.new(base_io, base_digest, digest_on_read: false)
+    io = OpenSSL::DigestIO.new(base_io, base_digest, OpenSSL::DigestIO::DigestMode::Write)
     slice = Bytes.new(256)
     io.read(slice).should eq(3)
     slice[0, 3].should eq("foo".to_slice)
@@ -41,7 +41,7 @@ describe OpenSSL::DigestIO do
   it "calculates digest from writing" do
     base_io = IO::Memory.new
     base_digest = OpenSSL::Digest.new("SHA256")
-    io = OpenSSL::DigestIO.new(base_io, base_digest)
+    io = OpenSSL::DigestIO.new(base_io, base_digest, OpenSSL::DigestIO::DigestMode::Write)
     io.write("foo".to_slice)
 
     base_io.to_slice[0, 3].should eq("foo".to_slice)
@@ -51,7 +51,7 @@ describe OpenSSL::DigestIO do
   it "calculates digest from writing a string" do
     base_io = IO::Memory.new
     base_digest = OpenSSL::Digest.new("SHA256")
-    io = OpenSSL::DigestIO.new(base_io, base_digest)
+    io = OpenSSL::DigestIO.new(base_io, base_digest, OpenSSL::DigestIO::DigestMode::Write)
     io.print("foo")
 
     base_io.to_slice[0, 3].should eq("foo".to_slice)
@@ -61,7 +61,7 @@ describe OpenSSL::DigestIO do
   it "calculates digest from multiple writes" do
     base_io = IO::Memory.new
     base_digest = OpenSSL::Digest.new("SHA256")
-    io = OpenSSL::DigestIO.new(base_io, base_digest)
+    io = OpenSSL::DigestIO.new(base_io, base_digest, OpenSSL::DigestIO::DigestMode::Write)
     io.write("fo".to_slice)
     io.write("o".to_slice)
     base_io.to_slice[0, 3].should eq("foo".to_slice)
@@ -73,7 +73,7 @@ describe OpenSSL::DigestIO do
     base_io = IO::Memory.new
     base_digest = OpenSSL::Digest.new("SHA256")
     empty_digest = OpenSSL::Digest.new("SHA256").digest
-    io = OpenSSL::DigestIO.new(base_io, base_digest, digest_on_write: false)
+    io = OpenSSL::DigestIO.new(base_io, base_digest, OpenSSL::DigestIO::DigestMode::Read)
     io.write("foo".to_slice)
 
     base_io.to_slice[0, 3].should eq("foo".to_slice)
diff --git a/src/openssl/digest/digest_io.cr b/src/openssl/digest/digest_io.cr
index e464581aa7eb..743b36dd752e 100644
--- a/src/openssl/digest/digest_io.cr
+++ b/src/openssl/digest/digest_io.cr
@@ -1,6 +1,6 @@
 require "./digest_base"
 
-# Wraps an IO by calculating a specified digest on read and/or write operations
+# Wraps an IO by calculating a specified digest on read or write operations
 #
 # ### Example
 #
@@ -20,30 +20,33 @@ module OpenSSL
 
     getter io : IO
     getter digest_algorithm : OpenSSL::Digest
-    getter digest_on_read : Bool
-    getter digest_on_write : Bool
+    getter mode : DigestMode
 
     delegate close, closed?, flush, peek, tty?, rewind, to: @io
-    delegate digest, to: @digest_algorithm
     delegate digest, hexdigest, base64digest, to: @digest_algorithm
 
-    def initialize(@io : IO, @digest_algorithm : OpenSSL::Digest, *, @digest_on_read = true, @digest_on_write = true)
+    enum DigestMode
+      Read
+      Write
     end
 
-    def initialize(@io : IO, algorithm : String, *, @digest_on_read = true, @digest_on_write = true)
+    def initialize(@io : IO, @digest_algorithm : OpenSSL::Digest, @mode = DigestMode::Read)
+    end
+
+    def initialize(@io : IO, algorithm : String, @mode = DigestMode::Read)
       @digest_algorithm = OpenSSL::Digest.new(algorithm)
     end
 
     def read(slice : Bytes)
       read_bytes = io.read(slice)
-      if @digest_on_read
+      if @mode == DigestMode::Read
         digest_algorithm.update(slice[0, read_bytes])
       end
       read_bytes
     end
 
     def write(slice : Bytes)
-      if @digest_on_write
+      if @mode == DigestMode::Write
         digest_algorithm.update(slice)
       end
       io.write(slice)