before:

null:00   ; oid=0..16995  nread=68269354  t=481.582632ms (28.335µs / object)  x=zsha1.go
null:00   ; oid=0..16995  nread=68269354  t=473.499859ms (27.859µs / object)  x=zsha1.go
null:00   ; oid=0..16995  nread=68269354  t=471.996668ms (27.771µs / object)  x=zsha1.go
null:00   ; oid=0..16995  nread=68269354  t=478.029272ms (28.125µs / object)  x=zsha1.go

after:

null:00   ; oid=0..16995  nread=68269354  t=709.761334ms (41.76µs / object)  x=zsha1.go
null:00   ; oid=0..16995  nread=68269354  t=704.768088ms (41.466µs / object)  x=zsha1.go
null:00   ; oid=0..16995  nread=68269354  t=720.756186ms (42.407µs / object)  x=zsha1.go
null:00   ; oid=0..16995  nread=68269354  t=693.688744ms (40.814µs / object)  x=zsha1.go

now we'll be teaching Recv1 & friends to do things in optimized way but Conn
functionality must stay working.