The net library has variables for well-known IPv6 addresses like the All Routers Addresses and All Nodes Addresses multicast addresses: https://golang.org/pkg/net/#pkg-variables

However it doesn't offer any convenience functions for converting an IPv6 address into a Solicited-Node Address multicast address.

Solicited-Node multicast address are computed as a function of a
node's unicast and anycast addresses. A Solicited-Node multicast
address is formed by taking the low-order 24 bits of an address
(unicast or anycast) and appending those bits to the prefix
FF02:0:0:0:0:1:FF00::/104 resulting in a multicast address in the
range
FF02:0:0:0:0:1:FF00:0000
to
FF02:0:0:0:0:1:FFFF:FFFF

Equally, when sending an ICMPv6 Neighbor Discovery request, the MAC address is also built by manipulating IPv6 address:

An IPv6 packet with a multicast destination address DST, consisting
of the sixteen octets DST[1] through DST[16], is transmitted to the
Ethernet multicast address whose first two octets are the value 3333
hexadecimal and whose last four octets are the last four octets of
DST.

It would be nice if there was a a function which accepted a argument of type net.IP, checked that the argument was IPv6, and returned the corresponding Ethernet multicast address as a net.HardwareAddr.