ARROW-2634: [Go] Add Go license details to LICENSE.txt

[wesm]

No description provided.

[wesm]

Note that Google's PATENTS file is a weak patent retaliation clause essentially equivalent (but IANAL) to the one in the Apache License 2.0 (https://www.apache.org/licenses/LICENSE-2.0).

Here is the ASL 2.0 patent termination clause (line breaks added for readability):

Subject to the terms and conditions of this License, each Contributor hereby
grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free,
irrevocable (except as stated in this section) patent license to make, have
made, use, offer to sell, sell, import, and otherwise transfer the Work, where
such license applies only to those patent claims licensable by such Contributor
that are necessarily infringed by their Contribution(s) alone or by combination
of their Contribution(s) with the Work to which such Contribution(s) was
submitted.

If You institute patent litigation against any entity (including a cross-claim
or counterclaim in a lawsuit) alleging that the Work or a Contribution
incorporated within the Work constitutes direct or contributory patent
infringement, then any patent licenses granted to You under this License for
that Work shall terminate as of the date such litigation is filed.

Here is Google's:

Google hereby grants to You a perpetual, worldwide, non-exclusive,
no-charge, royalty-free, irrevocable (except as stated in this section)
patent license to make, have made, use, offer to sell, sell, import,
transfer and otherwise run, modify and propagate the contents of this
implementation of Go, where such license applies only to those patent
claims, both currently owned or controlled by Google and acquired in
the future, licensable by Google that are necessarily infringed by this
implementation of Go.

This grant does not include claims that would be infringed only as a
consequence of further modification of this implementation.

If you or your agent or exclusive licensee institute or order or agree to the
institution of patent litigation against any entity (including a cross-claim or
counterclaim in a lawsuit) alleging that this implementation of Go or any code
incorporated within this implementation of Go constitutes direct or
contributory patent infringement, or inducement of patent infringement, then
any patent rights granted to you under this License for this implementation of
Go shall terminate as of the date such litigation is filed.

[wesm]

+1