[pid    24] accept4(3, {sa_family=AF_INET6, sin6_port=htons(55864), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::ffff:172.17.0.2", &sin6_addr), sin6_scope_id=0}, [112 => 28], SOCK_CLOEXEC|SOCK_NONBLOCK) = 8
[pid    24] getsockname(8, {sa_family=AF_INET6, sin6_port=htons(4122), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::ffff:172.17.0.3", &sin6_addr), sin6_scope_id=0}, [112 => 28]) = 0

Go
strace: Process 15 attached with 6 threads
[pid    21] restart_syscall(<... resuming interrupted io_setup ...> <unfinished ...>
[pid    15] futex(0x625dc0, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    26] futex(0x4000080148, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    27] futex(0x68c5b8, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    22] futex(0x400004b148, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    24] epoll_pwait(5, [{events=EPOLLIN, data={u32=4270850050, u64=18446565158232784898}}], 128, -1, NULL, 0) = 1
[pid    24] futex(0x6277e0, FUTEX_WAKE_PRIVATE, 1) = 1
[pid    21] <... restart_syscall resumed>) = 0
[pid    24] accept4(3, {sa_family=AF_INET6, sin6_port=htons(55864), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::ffff:172.17.0.2", &sin6_addr), sin6_scope_id=0}, [112 => 28], SOCK_CLOEXEC|SOCK_NONBLOCK) = 8
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    24] epoll_ctl(5, EPOLL_CTL_ADD, 8, {events=EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLET, data={u32=4238344195, u64=18446565158200279043}}) = 0
[pid    24] getsockname(8, {sa_family=AF_INET6, sin6_port=htons(4122), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "::ffff:172.17.0.3", &sin6_addr), sin6_scope_id=0}, [112 => 28]) = 0
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    24] setsockopt(8, SOL_TCP, TCP_NODELAY, [1], 4) = 0
[pid    24] setsockopt(8, SOL_SOCKET, SO_KEEPALIVE, [1], 4 <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    24] <... setsockopt resumed>)   = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    24] setsockopt(8, SOL_TCP, TCP_KEEPINTVL, [15], 4) = 0
[pid    24] setsockopt(8, SOL_TCP, TCP_KEEPIDLE, [15], 4) = 0
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] epoll_pwait(5, [{events=EPOLLIN|EPOLLOUT, data={u32=4238344195, u64=18446565158200279043}}], 128, 0, NULL, 0) = 1
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] getpid()                    = 15
[pid    21] tgkill(15, 24, SIGURG <unfinished ...>
[pid    24] futex(0x400004b148, FUTEX_WAKE_PRIVATE, 1) = 1
[pid    21] <... tgkill resumed>)       = 0
[pid    22] <... futex resumed>)        = 0
[pid    24] --- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=15, si_uid=0} ---
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    24] rt_sigreturn({mask=[]} <unfinished ...>
[pid    22] futex(0x625dc0, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid    24] <... rt_sigreturn resumed>) = 1
[pid    22] <... futex resumed>)        = 1
[pid    15] <... futex resumed>)        = 0
[pid    24] epoll_pwait(5, [], 128, 0, NULL, 0) = 0
[pid    15] epoll_pwait(5, [], 128, 0, NULL, 0) = 0
[pid    24] epoll_pwait(5,  <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    15] futex(0x625dc0, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    22] futex(0x625dc0, FUTEX_WAKE_PRIVATE, 1) = 1
[pid    15] <... futex resumed>)        = 0
[pid    15] nanosleep({tv_sec=0, tv_nsec=3000},  <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    22] accept4(3, 0x400015b27c, [112], SOCK_CLOEXEC|SOCK_NONBLOCK) = -1 EAGAIN (Resource temporarily unavailable)
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    15] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    15] futex(0x625dc0, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    22] read(8, "GET / HTTP/1.1\r\nHost: 172.17.0.3"..., 4096) = 79
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] getpid()                    = 15
[pid    21] tgkill(15, 22, SIGURG <unfinished ...>
[pid    22] futex(0x625dc0, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid    21] <... tgkill resumed>)       = 0
[pid    22] <... futex resumed>)        = 1
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    22] --- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=15, si_uid=0} ---
[pid    15] <... futex resumed>)        = 0
[pid    15] futex(0x4000080148, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid    26] <... futex resumed>)        = 0
[pid    15] <... futex resumed>)        = 1
[pid    22] rt_sigreturn({mask=[]} <unfinished ...>
[pid    26] futex(0x4000080148, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    22] <... rt_sigreturn resumed>) = 1
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    22] futex(0x400004b148, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000}, NULL) = 0
[pid    15] futex(0x400004b148, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    15] <... futex resumed>)        = 1
[pid    22] <... futex resumed>)        = 0
[pid    22] nanosleep({tv_sec=0, tv_nsec=3000},  <unfinished ...>
[pid    15] write(1, "GET /\n", 6)      = 6
[pid    22] <... nanosleep resumed>NULL) = 0
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    15] mmap(NULL, 262144, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 <unfinished ...>
[pid    22] futex(0x4000080148, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid    15] <... mmap resumed>)         = 0xffff5d42f000
[pid    22] <... futex resumed>)        = 1
[pid    26] <... futex resumed>)        = 0
[pid    26] futex(0x4000080148, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    22] read(8,  <unfinished ...>
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    22] <... read resumed>0x40001172d1, 1) = -1 EAGAIN (Resource temporarily unavailable)
[pid    22] futex(0x400004b148, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    15] write(8, "HTTP/1.1 200 OK\r\nContent-Type: t"..., 131) = 131
[pid    15] futex(0x400004b148, FUTEX_WAKE_PRIVATE, 1 <unfinished ...>
[pid    24] <... epoll_pwait resumed>[{events=EPOLLIN|EPOLLOUT|EPOLLRDHUP, data={u32=4238344195, u64=18446565158200279043}}], 128, -1, NULL, 0) = 1
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    15] <... futex resumed>)        = 1
[pid    22] <... futex resumed>)        = 0
[pid    24] epoll_pwait(5,  <unfinished ...>
[pid    22] epoll_pwait(5,  <unfinished ...>
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    24] <... epoll_pwait resumed>[], 128, 0, NULL, 0) = 0
[pid    22] <... epoll_pwait resumed>[], 128, 0, NULL, 0) = 0
[pid    24] nanosleep({tv_sec=0, tv_nsec=3000},  <unfinished ...>
[pid    15] read(8,  <unfinished ...>
[pid    22] epoll_pwait(5,  <unfinished ...>
[pid    15] <... read resumed>"", 1)    = 0
[pid    15] read(8,  <unfinished ...>
[pid    24] <... nanosleep resumed>NULL) = 0
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    15] <... read resumed>"", 4096) = 0
[pid    24] futex(0x400004b948, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] nanosleep({tv_sec=0, tv_nsec=20000},  <unfinished ...>
[pid    15] epoll_ctl(5, EPOLL_CTL_DEL, 8, 0x40002b9228) = 0
[pid    15] close(8)                    = 0
[pid    15] futex(0x625dc0, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid    21] <... nanosleep resumed>NULL) = 0
[pid    21] futex(0x6277e0, FUTEX_WAIT_PRIVATE, 0, {tv_sec=60, tv_nsec=0}
