I had never tried because there is no information about building Sia on FreeBSD, so I decided to try to build renterd... and it works !
First, install go :
pkg ins -y go git
Download Linux sources of Sia :
cd /tmp
git clone https://github.com/SiaFoundation/renterd.git
cd renterd/
Download go dependancies :
go build ./...
Repeat :
go build ./...
Build renterd :
cd /tmp/renterd/cmd/renterd/
go build
./renterd appears.
Don't try to start it before setting the owner.
Move to /usr/local/ :
mkdir -p /usr/local/renterd
mv /tmp/renterd /usr/local/renterd/src
Set the owner:
chown -R YOURUSER:wheel /usr/local/renterd
Create a symbolic link :
ln -s /usr/local/renterd/src/cmd/renterd/renterd /usr/bin/renterd
Let's go back to normal user :
./renterd
After creating a password and putting your seed, open your web browser
http://127.0.0.1:9980
The blockchain will start downloading. I did not wait until the end.. too long :-D...